Liquid crystal device and electronic device having liquid crystal molecules aligned at reflective electrodes

ABSTRACT

When a backlight  15  is turned on in a dark environment, white light emerging from the surface of a light guide plate  15   b  passes through a polarizer  12  and a retardation film  14,  enters the interior of the liquid crystal cell, passes through openings of reflective electrodes  7,  and is introduced into a liquid crystal layer  3.  The light introduced into the liquid crystal layer  3  passes through a color filter  5,  emerges from the liquid crystal cell, and passes through the retardation film  13  and the polarizer  11  towards the exterior. In a lighted environment, the light incident on the polarizer  11  passes through the liquid crystal layer  3,  is reflected by the reflective electrode  7,  and passes through the polarizer  11  again and is emitted towards the exterior.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. Ser. No. 11/457,175 filed Jul.13, 2006 which is a continuation of U.S. Ser. No. 10/368,191 filed onFeb. 18, 2003, which is a divisional of U.S. Ser. No. 09/402,557 filedOct. 4, 1999, now U.S. Pat. No. 6,628,357, which is a U.S. NationalPhase of PCT/JP99/00311 filed Jan. 26, 1999, which claims priority toJP10-023656 filed Feb. 4, 1998 and JP10-157622 filed Jun. 5, 1998. Thedisclosures of the above applications are incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to the technical field of liquid crystaldevices. In particular, the present invention relates to a structure ofa liquid crystal device which can change a display mode between areflective mode and a transmissive mode, and to an electronic deviceusing the liquid crystal device.

2. Background Art

Reflective liquid crystal devices consuming small amounts of electricalpower have been widely used in portable devices and display sections invarious apparatuses. Since, however, the display is performed byexternal light, an image is not visible in dark environments. Thus, someproposed liquid crystal devices use external light in a lightedenvironment as in general reflective liquid crystal devices, and aninternal light source in dark environments so as to maintain a visiblestate. As disclosed in Japanese Patent Application Laid-Open Nos.57-049271, 57-049271, and 57-049271, each device has a polarizer, atransflector, and a backlight, in that order, at the outer face, awayfrom the viewer, in a liquid crystal panel. The liquid crystal deviceperforms reflective display using external light reflected by thetransflector in a lighted environment, and transmissive display usinglight from the backlight, which is turned on so as to maintain a visiblestate, transmitted through the transflector in dark environments.

Another liquid crystal device having improved brightness in a reflectivedisplay mode is disclosed in Japanese Patent Application Laid-Open No.8-292413. The liquid crystal device has a transflector, a polarizer, anda backlight, in that order, at the outer face, away from the viewer, ofthe liquid crystal panel. The device performs reflective display usingexternal light reflected by the transflector when the environment islight, and transmissive display using light from the backlight, which isturned on so as to maintain a visible state, transmitted through thepolarizer and the transflector. Since the polarizer is not providedbetween the liquid crystal cell and the transflector, brighter displayis achieved in a reflective mode compared to the above-mentioned liquidcrystal devices.

In the liquid crystal device disclosed in Japanese Patent ApplicationLaid-Open No. 8-292413, however, a transparent substrate is disposedbetween a liquid crystal layer and the transflector; hence, problems,such as double imaging and blurred imaging, occur.

Color liquid crystal display has been required with recent developmentof portable devices and office automation devices. Apparatuses usingreflective liquid crystal devices also require color display. In acombination of the liquid crystal device disclosed in the above patentapplication with a color filter, the transfiector is arranged behind theliquid crystal panel. Thus, the thick transparent substrate lies betweenthe liquid crystal layer with the color filter and the transflector,resulting in occurrence of double imaging or blurred imaging due toparallax and insufficient coloring.

In order to solve the problems, Japanese Patent Application Laid-OpenNo. 9-258219 discloses a reflective color liquid crystal device in whicha reflector is disposed so as to come into contact with the liquidcrystal layer. This liquid crystal device, however, cannot displayvisible images in dark environments.

In addition, Japanese Patent Application Laid-Open No. 7-318929discloses a transflective liquid crystal device in which a pixelelectrode functioning as a transflective film is provided on the innerface of the liquid crystal cell. Since this liquid crystal device has atransflective film such as a metallic thin film having fine defectsincluding pinholes, dimples, and fine openings, an oblique electricfield which is generated on the periphery of the defects and openingscauses unsatisfactory orientation of the liquid crystal, producing manytechnical problems which inhibit high-quality image display. That is, ahigh contrast and brightness are not achieved, and coloring due towavelength dispersion of light inevitably occurs both in a reflectivedisplay mode and a transmissive display mode. Furthermore, it isdifficult to achieve both prevention of brightness defects at the gapbetween pixel electrodes or an improvement in contrast and animprovement in brightness in a reflective display mode. Furthermore, theproduction process requires addition of a particular step; hence, thedevice satisfies with great difficulty a typical demand for reduction inproduction cost in this technical field.

The present invention has been accomplished in view of theabove-mentioned problems and has an object to provide a transflectiveliquid crystal device, which is changeably used both in a reflectivedisplay mode and a transmissive display mode, does not produce doubleimaging blurred imaging due to parallax, and can display high-qualityimages, and to provide an electronic apparatus using the liquid crystaldevice.

SUMMARY OF THE INVENTION

The object of the present invention is achieved by a first liquidcrystal device including a pair of first and second transparentsubstrates; a liquid crystal layer disposed between the first and secondsubstrates; a transparent electrode formed on a face of the firstsubstrate, on the side of the liquid crystal layer; a reflectiveelectrode formed on a face of the second substrate and having an oblongslit, the face contacting the liquid crystal layer; and an illuminationunit provided on another face of the second substrate, on the oppositeside of the liquid crystal layer.

In accordance with the first liquid crystal device of the presentinvention, the reflective electrode reflects external light incident onthe first substrate towards the liquid crystal layer in a reflectivedisplay mode. Since the reflective electrode is provided on the liquidcrystal layer face of the second substrate, no gap is substantiallyformed between the liquid crystal layer and the reflective electrode andthus double imaging and blurred imaging due to parallax do not occur. Ina transmissive display mode, illuminated light incident on the secondsubstrate from the illumination unit enters the liquid crystal layerthrough the slits. Thus, the illuminated light enables bright display indark environments.

Since the reflective electrode has oblong slits, an oblique electricfield (hereinafter referred to as an “oblique electric field due to theshort sides of the slit”) is applied to the liquid crystal layer betweenthe edges of each reflective electrode defining short sides of a slitand opposingly disposed at a relatively large distance (edges of eachreflective electrode opposing each other at each end of two long sidesof a slit) and the transparent electrode. An oblique electric field(hereinafter referred to as an “oblique electric field due to the longsides of the slit”) is simultaneously applied to the liquid crystallayer between edges of each reflective electrode defining long sides ofa slit and opposingly disposed at a relatively short distance (edges ofeach reflective electrode opposing each other at each end of two shortsides of a slit) and the transparent electrode. The components of theoblique electric field due to the short sides of the slit and the sameof the oblique electric field due to the long sides of the slit areperpendicular to each other in the substrate plane. When these twooblique electric fields interact with liquid crystal molecules in thevicinity of the slit, the intensities of these two oblique electricfields determine the direction of movement of liquid crystal molecules.If the slit is a square, these two oblique electric fields areequivalent to each other. Thus, the relationship between theseintensities is reversed at some positions. As a result, the directionsof movement of liquid crystal molecules are different at thesepositions, and insufficient alignment of the liquid crystal appears as arelatively large domain. That is, display defects occur in the domain.Insufficient alignment is most noticeable when these two obliqueelectric fields have the same intensity. If one is higher than the otherin a region, movement of liquid crystal molecules in the region iscontrolled by the oblique electric field having a higher intensity andthus becomes uniform. In the present invention, the oblique electricfield (the in-substrate-plane component is parallel to the longitudinaldirection of the slit) due to the short sides of the slit is reduced inresponse to the length of long sides of the slit. In contrast, theoblique electric field (the in-substrate-plane component isperpendicular to the longitudinal direction of the slit) due to the longsides of a slit is relatively increased in response to the length of theshort sides of the slit. In the present invention, therefore, theoblique electric field due to the long sides of the slit controls themovement of liquid crystal molecules. Accordingly, insufficientalignment is reduced in the vicinity of the slit and display defects arereduced. Furthermore, electrical power consumed by the liquid crystaldevice can be reduced by a reduced threshold voltage, since the liquidcrystal is partly driven using the oblique electric field due to thelong sides of the slit.

When a countermeasure is taken only for the oblique electric field dueto the long side of the slit, and no consideration is given to theoblique electric field due to the short side of the slit, overallinsufficient alignment of the liquid crystal caused by the obliqueelectric field can be reduced. Alternatively, voluntary use of theoblique electric field (for example, setting of various operationalparameters for reducing adverse effects of insufficient alignment of theliquid crystal caused by the oblique electric field in practice or forsatisfactorily driving of the liquid crystal by the oblique electricfield, setting of specifications of constituents and parts, and devicedesign) facilitates satisfactory driving of the liquid crystal. If theslit is square, countermeasures must be taken for two oblique electricfields, resulting in very difficult design and production of the liquidcrystal device. Furthermore, voluntary use of these two oblique electricfields is almost impossible in practice.

As materials for the reflective electrode, metals containing aluminum asa primary component are used. Metals which can reflect external visiblelight, such as chromium and silver, can also be used without limitation.Since the reflective electrode has a function of reflecting externallight and a function of applying a voltage to the liquid crystal, thisdevice structure has advantages in production and design and facilitatescost reduction compared to a structure having independently formedreflective electrodes and pixel electrodes.

Oblong slits can be readily formed by a photostep using a resist, adevelopment step, and then a peeling step. It means that there is noneed to increase the number of production processes since the slits canbe simultaneously formed when the reflective electrodes are formed. Thewidth of each slit is in a range of preferably 0.01 μm to 20 μm, and ismore preferably 1 μm to 5 μm. Thus, a reflective display mode and atransmissive display mode can be simultaneously achieved withoutdeterioration of image quality due to provision of the slit, since aviewer cannot recognize such a structure. Preferably, the slit has anarea ratio of 5% to 30% with respect to the reflective electrode. Such aratio can moderate decreased brightness in a reflective display mode,and achieves a transmissive display mode by light incident on the liquidcrystal layer via the slits of the reflective electrodes.

The first liquid crystal device can be driven by various conventionaldriving system, such as a passive matrix driving system, a thin filmtransistor (TFT) active matrix driving system, a thin film diode (TFD)active matrix driving system, or a segment driving system.

In an embodiment of the first liquid crystal device in accordance withthe present invention, the reflective electrode comprises a plurality ofstripe electrodes at a predetermined gap and the slit extends in thelongitudinal direction of the reflective electrode.

According to this embodiment, a countermeasure for the oblique electricfield caused by the long sides of the slit is effective for the obliqueelectric field caused by gaps between the reflective electrodes.Furthermore, the reflective electrodes and the slits can besimultaneously formed, and the design of the mask used in the formationcan be simplified. Thus, this embodiment has advantages in a structure,production, and design of the device.

In this embodiment in which the stripe reflective electrodes are formedin stripe, the transparent electrode may comprise a plurality of stripeelectrodes at a predetermined gap in the direction perpendicular to thereflective electrode and the slit may extend to a position facing thegap between the transparent electrodes.

In such a structure, edges of each reflective electrode defining shortsides of each slit and opposingly disposed at a relatively largedistance lie in a position in which the transparent electrode is notformed. That is, the edges lie distant from a portion of the reflectiveelectrode in which a voltage is applied between the transparentelectrode and the reflective electrode. Thus, the effect of the obliqueelectric field due to the short side of the slit can be significantlyreduced.

In this embodiment in which the reflective electrodes are formed instripe, the slit may extend over a plurality of pixels.

In such a structure, each pixel does not have edges of reflectiveelectrodes defining short sides of slits opposingly disposed at arelatively large distance; hence, the effect of the oblique electricfield which is applied to the liquid crystal layer between the edges ofthe reflective electrode and the transparent electrode due to the shortside (a shorter side is preferable) of the slit can be significantlyreduced.

In this case, the slit may extend to the exterior of the image displayregion.

In such a structure, each pixel does not have edges of reflectiveelectrodes defining short sides of slits opposingly disposed at arelatively large distance; hence, the effect of the oblique electricfield due to the short side (a shorter side is preferable) of the slitcan be almost completely reduced.

In this embodiment in which electrodes are formed in stripe, the widthof a slit may be substantially equal to a gap between reflectiveelectrodes.

In such a structure, a countermeasure for or voluntary use of, theoblique electric field due to the long side of the slit is alsoeffective as a countermeasure for or voluntary use of, the obliqueelectric field due to the gap between the reflective electrodes.Furthermore, the slits can be simultaneously formed when the reflectiveelectrodes are formed and design of the photomask is simplified; hencethis structure has significant advantages in production and design ofthe device. Herein “substantially equal” means that the width of a slitis almost equal to the gap between the reflective electrodes so that theeffect of the oblique electric field due to the long side of the slitand the effect of the oblique electric field caused by the gap betweenthe reflective electrodes appear equally, or almost equal enough thatthey can be formed utilizing photomasks having the same width.

In another embodiment of the first liquid crystal device in accordancewith the present invention, the width of the slit is 4 μm or less.

As a result of experiments and research by the present inventors, thevariation of the threshold voltage of the liquid crystal with the widthof the slit was elucidated. Specifically, when the slit width is largerthan 4 μm, the threshold voltage of the liquid crystal significantlydiffers between the reflective display mode and the transmissive displaymode; hence, it is difficult or impossible to set a driving voltageenabling a satisfactory contrast and a variation of density in bothdisplay modes. When the width of the slit is larger than 4 μm, a highintensity electric field would likely be necessary to drive the liquidcrystal facing the slit. Since the width of the slit is 4 μm or less inthis embodiment, the threshold voltage of the liquid crystal can be setto be substantially the same in both the reflective display mode and thetransmissive display mode. For example, when the width of the slit is 2μm and the width of the reflective electrode is 10 μm, a driving voltagefacilitating a high contrast and a large change in density can bereadily set.

In another embodiment of the first liquid crystal device in accordancewith the present invention, an angle ξ between the alignment directionof the liquid crystal molecule substantially in the center between thetransparent electrode and the reflective electrode and the longitudinaldirection of the slit is in a range of −60°≦ξ≦60°.

According to this embodiment, the angle between the alignment directionof liquid crystal molecules, which lie substantially in the centerbetween the transparent electrode and the reflective electrode and havethe highest mobility, and the longitudinal direction of the slit shiftsby 30° or more from a right angle. Thus, when a voltage is appliedbetween the transparent electrode and the reflective electrode, thealignment state of the liquid crystal molecules changes satisfactorilywith almost no formation of a tilt domain. Thus, the threshold voltageduring driving of the liquid crystal can be reduced, resulting inreduced power consumption of the liquid crystal device. Furthermore,display defects, such as disclination due to the tilt domain in theliquid crystal layer, are avoidable. A significant tilt domain isgenerated if the angle ξ is outside the range of −60°≦ξ≦60°, because thealignment direction of the liquid crystal molecules is perpendicular tothe longitudinal direction of the slit. Thus, the driving voltageincreases. The above advantage is particularly noticeable in a range of−30°≦ξ≦30°. The tilt domain is the same as the phenomenon described in“Liquid Crystal Device Handbook”, p. 254, edited by Committee 142 inJapan Society for the Promotion of Science, and published by The DailyIndustrial News. The tilt domain in the present invention, however, isgenerated by the direction of the applied voltage, not by the pretiltangle.

In another embodiment of the first liquid crystal device of the presentinvention, an angle δ between the alignment direction of a liquidcrystal molecule in the vicinity of the reflective electrode and thelongitudinal direction of the slit is in a range of −30°≦δ≦30°.

According to this embodiment, the alignment direction of the liquidcrystal molecule in the vicinity of the reflective electrode having apredetermined pretilt angle is nearly parallel to, rather thanperpendicular to, the longitudinal direction of the slit. Thus, there issubstantially no possibility of the liquid crystal molecule at thesubstrate interface being reverse-tilted by the effect of the obliqueelectric field. Display defects such as disclination due to the reversetilt domain are, therefore, avoidable. Thus, the threshold voltageduring driving of the liquid crystal can be reduced, resulting inreduced power consumption of the liquid crystal device. If the angle δis in a range outside −30°≦δ≦30°, the liquid crystal molecule at thesubstrate interface is noticeably reverse-titled by the effect of theoblique electric field causing display defects. Furthermore, the drivingvoltage increases, resulting in increased power consumption. The aboveadvantage is particularly noticeable in a range of −10°≦δ≦10°.

In another embodiment of the first liquid crystal device in accordancewith the present invention, the device is in a dim or black state whennot driven.

Since the device is in a dim or black state when not driven in thisembodiment, optical leakage from boundaries between non-driven liquidcrystal pixels or dots can be reduced in a transmissive display mode,resulting in transmissive display having a high contrast. Furthermore,undesirable reflection at boundaries between pixels or dots can bereduced in a reflective display mode, resulting in a display having ahigh contrast.

In another embodiment of the first liquid crystal device in accordancewith the present invention, a shading layer is formed on at least one ofthe face of the first substrate, on the side of the liquid crystal layerand the face of the second substrate, on the side of the liquid crystallayer, so as to at least partly cover the gap between the reflectiveelectrodes.

According to this embodiment, optical leakage from boundaries betweennon-driven liquid crystal pixels or dots can be reduced in atransmissive display mode, resulting in transmissive display having ahigh contrast. Furthermore, undesirable reflection at boundaries betweenpixels or dots can be reduced in a reflective display mode, resulting ina display having a high contrast.

In another embodiment of the first liquid crystal device in accordancewith the present invention, the device further includes a firstpolarizer provided on another face of the first substrate, on theopposite side of the liquid crystal layer, and at least one firstretardation film disposed between the first substrate and the firstpolarizer.

According to this embodiment, the first polarizer primarily achievessatisfactory display control in both the reflective and transmissivedisplay modes, and the first retardation film primarily reduces effectson tonality, such as coloring, due to the wavelength dispersion oflight.

In another embodiment of the first liquid crystal device in accordancewith the present invention, the device further includes a secondpolarizer disposed between the second substrate and the illuminationunit, and at least a second retardation film disposed between the secondsubstrate and the second polarizer.

According to this embodiment, the second polarizer primarily achievessatisfactory display control in the transmissive display mode, and thesecond retardation film primarily reduces effects on tonality, such ascoloring, due to the wavelength dispersion of light.

In another embodiment of the first liquid crystal device in accordancewith the present invention, the reflective electrode contains 95% byweight or more of aluminum and has a thickness of 10 nm to 40 nm.

According to this embodiment, a thin transflective type reflectiveelectrode is formed. According to experiments, the transflectivereflective electrode has a transmittance of 1% to 40% and a reflectance50% to 95% within the above thickness range.

In another embodiment of the first liquid crystal device in accordancewith the present invention, the device further includes a color filterprovided between the reflective electrode and the first substrate.

According to this embodiment, reflective color display by external lightand transmissive color display using an illumination unit are available.Preferably, the color filter has a transmittance of 25% or more forlight of any wavelength within a range of 380 nm to 780 nm. Brightreflective and transmissive color display is thereby achieved.

In another embodiment of the first liquid crystal device in accordancewith the present invention, the device further includes a diffuser onanother face of the first substrate, on the opposite side of the liquidcrystal layer.

According to this embodiment, the diffuser makes the mirror face of thereflective electrode look as a diffusing face (white surface). Diffusionby the diffuser enables display with a wide view angle. The diffuser maybe disposed at any position above the face of the first substrate, onthe opposite side of the liquid crystal layer. Preferably, the diffuseris disposed between the polarizer and the first substrate inconsideration of the effect of back scattering (scattering of theexternal light towards the incident side of it). The back scattering notcontributing to the display of the liquid crystal device causes adecreased contrast in a reflective display mode. When the diffuser isdisposed between the polarizer and the first substrate, the polarizercan reduce the quantity of light of back scattering to approximatelyone-half.

In another embodiment of the first liquid crystal device in accordancewith the present invention, the reflective electrode has irregularities.

According to this embodiment, the irregularities eliminate the mirroringon the face of the reflective electrode and make the mirror face look asa diffusing face (white face). Diffusion by the irregularities enablesdisplay with a wide view angle. The irregularities may be formed byforming a photosensitive acrylic resin layer under the reflectiveelectrode, or by roughening the underlying glass substrate with aqueoushydrogen fluoride. It is preferable in order to achieve satisfactoryalignment of the liquid crystals that a transparent planarization filmbe formed on the irregular surface of the reflective electrode so thatthe surface contacting the liquid crystal layer (the surface on which analignment film is formed) is planarized.

In another embodiment of the first liquid crystal device in accordancewith the present invention, the reflective electrode is a composite of areflective layer and a transparent electrode layer.

According to this embodiment, even if the reflective electrode withslits is not composed of a reflective and conductive single film, thereflective electrode can be obtained by making the reflective layerreflect external light, and the transparent electrode layer apply adriving voltage to the liquid crystal.

The above-mentioned object of the present invention is also achieved bya first electronic apparatus provided with the first liquid crystaldevice.

The first electronic apparatus in accordance with the present inventionuses a transflective liquid crystal device or a color transflectiveliquid crystal device without double imaging and blurred imaging due toparallax, and can change a display mode between a reflective mode and atransmissive mode. Thus, the electronic apparatus can displayhigh-quality images in any lighted or dark environment regardless of thelevel of ambient or external light.

The object of the present invention is also achieved by a second liquidcrystal device including a pair of first and second transparentsubstrates; a liquid crystal layer disposed between the first and secondsubstrates; a transparent electrode formed on a face of the liquidcrystal layer side of the first substrate; a reflective electrode formedon a face of the liquid crystal layer side of the second substrate; anillumination unit provided on another face of the second substrate, onthe opposite side of the liquid crystal layer; a first polarizerprovided on another side of the first substrate, on the opposite side ofthe liquid crystal layer; at least one first retardation film disposedbetween the first substrate and the first polarizer; a second polarizerdisposed between the second substrate and the illumination unit; and atleast a second retardation film disposed between the second substrateand the second polarizer.

According to the second liquid crystal device of the present invention,the reflective electrode reflects external light incident on the firstsubstrate towards the liquid crystal layer in a reflective display mode.Since the reflective electrode is provided on the face of the secondsubstrate, contacting the liquid crystal layer, no gap is substantiallyformed between the liquid crystal layer and the reflective electrode.Thus, double imaging and blurred imaging due to parallax do not occur.On the other hand, the reflective electrode comprising a transflectivelayer transmits light which emerges from the illumination unit and isincident on the second substrate towards the liquid crystal layer in atransmissive display mode. Thus, light from the light source achievesbright display in a dark environment. The transflective layer may be areflective film having oblong slits or square fine openings so thatlight partly passes through the film, as in the above-mentioned firstliquid crystal of the present invention, a thin metal transflective filmhaving fine defects, such as pinhole defects or dimples, or a film whichshows overall transflective characteristics. Alternatively, the layermay be composed of a plurality of stripes or island reflectiveelectrodes formed with a predetermined gap.

Since the second liquid crystal device has the first polarizer, thefirst retardation film, the second polarizer, and the second retardationfilm, the first and the second polarizers satisfactorily control displayin both the reflective and transmissive display modes. The firstretardation film reduces effects on tonality, such as coloring, due tothe wavelength dispersion of light in a reflective display mode, whereasthe second retardation film reduces effects on tonality, such ascoloring, due to the wavelength dispersion of light in a transmissivedisplay mode. The second liquid crystal device can be driven by variousconventional driving system, such as a passive matrix driving system, aTFT active matrix driving system, a TFD active matrix driving system, ora segment driving system.

In an embodiment of the second liquid crystal device of the presentinvention, the device is in a dim or black state when not driven.

Since the device is in a dim or black state when not driven in thisembodiment, optical leakage from boundaries between non-driven liquidcrystal pixels or dots can be reduced in a transmissive display mode,resulting in transmissive display having a high contrast. Furthermore,undesirable reflection at boundaries between pixels or dots can bereduced in a reflective display mode, resulting in a display having ahigh contrast.

In another embodiment of the second liquid crystal device in accordancewith the present invention, a shading layer is formed on at least one ofthe face of the first substrate, on the side of the liquid crystal layerand the face of the second substrate, contacting the liquid crystallayer so as to at least partly cover the gap between the reflectiveelectrodes.

According to this embodiment, optical leakage from boundaries betweennon-driven liquid crystal pixels or dots can be reduced in atransmissive display mode, resulting in transmissive display having ahigh contrast. Furthermore, undesirable reflection, which does notcontribute to the display, at boundaries between pixels or dots can bereduced in a reflective display mode, resulting in a display having ahigh contrast.

In another embodiment of the second liquid crystal device in accordancewith the present invention, the reflective electrode contains 95% byweight or more of aluminum and has a thickness of 10 nm to 40 nm.

According to this embodiment, a thin transflective type reflectiveelectrode is formed. According to experiments, the transflective typereflective electrode has a transmittance of 1% to 40% and a reflectance50% to 95% within the above thickness range.

In another embodiment of the second liquid crystal device in accordancewith the present invention, the device further includes a color filterprovided between the reflective electrode and the first substrate.

According to this embodiment, reflective color display by external lightand transmissive color display using an illumination unit are available.Preferably, the color filter has a transmittance of 25% or more forlight of any wavelength within a range of 380 nm to 780 nm. Brightreflective and transmissive color displays are thereby achieved.

In another embodiment of the second liquid crystal device in accordancewith the present invention, the device further includes a diffuser onanother face of the first substrate, on the opposite side thereof theliquid crystal layer.

According to this embodiment, the diffuser makes the mirror face of thereflective electrode look as a diffusing face (white surface). Diffusionby the diffuser enables display with a wide view angle. The diffuser maybe disposed at any position above the face of the first substrate, onthe opposite side of the liquid crystal layer. Preferably, the diffuseris disposed between the polarizer and the first substrate inconsideration of the effect of back scattering (scattering of theexternal light towards the incident side of it). The back scattering notcontributing to the display of the liquid crystal device causes adecreased contrast in a reflective display mode. When the diffuser isdisposed between the polarizer and the first substrate, the polarizercan reduce the quantity of light of back scattering to approximatelyone-half.

In another embodiment of the second liquid crystal device in accordancewith the present invention, the reflective electrode has irregularities.

According to this embodiment, the irregularities eliminate the mirroringon the face of the reflective electrode and render the mirror face intoa diffusing face (white face). Diffusion by the irregularities enablesdisplay with a wide view angle. The irregularities may be formed byforming a photosensitive acrylic resin layer under the reflectiveelectrode, or by roughening the underlying glass substrate with aqueoushydrogen fluoride. It is preferable in order to achieve satisfactoryalignment of the liquid crystals that a transparent planarization filmbe formed on the irregular surface of the reflective electrode so thatthe surface facing to the liquid crystal layer (the surface on which analignment film is formed) is planarized.

In another embodiment of the second liquid crystal device in accordancewith the present invention, the reflective electrode is a composite of areflective layer and a transparent electrode layer.

According to this embodiment, the reflective layer reflects externallight, and the transparent electrode layer applies a driving voltage tothe liquid crystal even if the reflective electrode is not composed of areflective and conductive single film.

The above-mentioned object of the present invention is also achieved bya second electronic apparatus provided with the second liquid crystaldevice.

The second electronic apparatus in accordance with the present inventionuses a transflective liquid crystal device or a color transflectiveliquid crystal device without double imaging and blurred imaging due toparallax, and can change a display mode between a reflective mode and atransmissive mode. Thus, the electronic apparatus can displayhigh-quality images in any lighted or dark environment regardless of thelevel of ambient or external light.

The object of the present invention is also achieved by a third liquidcrystal device including a pair of first and second transparentsubstrates; a liquid crystal layer disposed between the first and secondsubstrates; a plurality of reflective electrodes with a predeterminedgap formed on a face of the second substrate, on the side of the liquidcrystal layer; a transparent electrode formed on a face of the firstsubstrate, on the side of the liquid crystal layer, and opposing to thereflective electrodes and gaps between the reflective electrodes; and anillumination unit provided on an another face of the second substrate,on the opposite side of the liquid crystal layer.

According to the third liquid crystal device of the present invention,the reflective electrode reflects external light incident on the firstsubstrate towards the liquid crystal layer in a reflective display mode.Since the reflective electrode is provided on the face of the secondsubstrate, on the side of the liquid crystal layer, no gap issubstantially formed between the liquid crystal layer and the reflectiveelectrode. Thus, double imaging and blurred imaging due to parallax donot occur. On the other hand, light which is incident on the secondsubstrate passes through a gap between the reflective electrodes and isincident on the liquid crystal layer in a transmissive display mode.Herein, an oblique electric field generated between a portion of thetransparent electrode facing the gap between the reflective electrodes,and the reflective electrode can drive the liquid crystal. Thus, lightfrom the light source which passes through the gap between thereflective electrodes is driven by the oblique electric field tofacilitate bright display. Whitening by non-driven liquid crystalportions facing the gap between the reflective electrodes can besimultaneously prevented, and thus display defects due to the gapbetween the reflective electrodes can be reduced. Since covering the gapbetween the reflective electrodes with a shading film (called a “blackmatrix” or a “black mask”) is not necessary, this structure hasadvantages in production and design of the device.

The third liquid crystal device can be driven by various conventionaldriving system, such as a passive matrix driving system, a TFT activematrix driving system, a TFD active matrix driving system, or a segmentdriving system. Thus, the reflective electrodes may be composed of aplurality of stripe electrodes or a plurality of rectangular electrodesdepending on the applied driving system.

The width of the gap between the reflective electrodes is in a range ofpreferably 0.01 μm to 20 μm, and is more preferably 1 μm to 5 μm. Areflective display mode and a transmissive display mode can besimultaneously achieved without deterioration of image quality due toprovision of the gap, since a viewer cannot recognize such a structure.Preferably, the gap has an area ratio of 5% to 30% with respect to thereflective electrode. Such a ratio can moderate decreased brightness ina reflective display mode, and achieves a transmissive display mode bylight incident on the liquid crystal layer via the gap between thereflective electrodes. In the transmissive display mode, brighthigh-quality display by the liquid crystal at the gap portion isachieved by increasing luminance of the light source in the illuminationunit, even if only a small portion of the overall liquid crystal isdriven by the oblique electric field.

In an embodiment of the third liquid crystal in accordance with thepresent invention, a plurality of long reflective electrodes is formed,and an angle φ between the alignment direction of liquid crystalmolecules, which lie substantially in the center between the transparentelectrode and the reflective electrodes, and the longitudinal directionof the reflective electrodes is in a range of −60°≦φ≦60°.

According to this embodiment, long reflective electrodes, such asstripe- or rectangular-reflective electrodes, are formed, and the anglebetween the alignment direction of liquid crystal molecules, which liesubstantially in the center between the transparent electrode and thereflective electrode and have the highest mobility, and the longitudinaldirection of the reflective electrode shifts by 30° or more from a rightangle. When a voltage is applied between the transparent electrode andthe reflective electrode, the alignment state of the liquid crystalmolecules changes satisfactorily without formation of a tilt domain.Thus, the threshold voltage during driving of the liquid crystal can bereduced, resulting in reduced power consumption of the liquid crystaldevice. Furthermore, display defects, such as disclination, due to thetilt domain in the liquid crystal layer, are avoidable. A significanttilt domain is generated if the angle φ is outside the range of−60°≦φ≦60°, because the alignment direction of the liquid crystalmolecules is perpendicular to the longitudinal direction of thereflective electrode. Thus, the driving voltage increases. The aboveadvantage is particularly noticeable in a range of −30°≦φ≦30°.

In another embodiment of the third liquid crystal device of the presentinvention, an angle ψ between the alignment direction of a liquidcrystal molecule in the vicinity of the reflective electrode and thelongitudinal direction of the reflective electrode is in a range of−30°≦ψ≦30°.

According to this embodiment, the alignment direction of the liquidcrystal molecule in the vicinity of the reflective electrode having apredetermined pretilt angle is nearly parallel to, rather thanperpendicular to, the longitudinal direction of the reflectiveelectrode. Thus, there is substantially no possibility of the liquidcrystal molecule at the substrate interface being reverse-tilted by theeffect of the oblique electric field. Display defects such asdisclination due to the reverse tilt domain are, therefore, avoidable.Thus, the threshold voltage during driving of the liquid crystal can bereduced, resulting in reduced power consumption of the liquid crystaldevice. If the angle ψ is in a range outside −30°≦ψ≦30°, the liquidcrystal molecule at the substrate interface is noticeably reverse-titledby the effect of the oblique electric field to cause display defects.Furthermore, the driving voltage increases, resulting in increased powerconsumption. The above advantage is particularly noticeable in a rangeof −10°≦ψ≦10°.

In another embodiment of the third liquid crystal device in accordancewith the present invention, the device further includes a firstpolarizer provided on another face of the first substrate, away from theliquid crystal layer, and at least one first retardation film disposedbetween the first substrate and the first polarizer.

According to this embodiment, the first polarizer primarily achievessatisfactory display control in both the reflective and transmissivedisplay modes, and the first retardation film primarily reduces effectson tonality, such as coloring, due to the wavelength dispersion oflight.

In another embodiment of the third liquid crystal device in accordancewith the present invention, the device further includes a secondpolarizer disposed between the second substrate and the illuminationunit, and at least a second retardation film disposed between the secondsubstrate and the second polarizer.

According to this embodiment, the second polarizer primarily achievessatisfactory display control in the transmissive display mode, and thesecond retardation film primarily reduces effects on tonality, such ascoloring, due to the wavelength dispersion of light.

In another embodiment of the third liquid crystal device in accordancewith the present invention, the reflective electrode contains 95% byweight or more of aluminum and has a thickness of 10 nm to 40 nm.

According to this embodiment, a thin transflective type reflectiveelectrode is formed. According to experiments, the transflective typereflective electrode has a transmittance of 1% to 40% and a reflectance50% to 95% within the above thickness range.

In another embodiment of the third liquid crystal device in accordancewith the present invention, the device further includes a color filterprovided between the reflective electrode and the first substrate.

According to this embodiment, reflective color display by external lightand transmissive color display using an illumination unit are available.Preferably, the color filter has a transmittance of 25% or more forlight of any wavelength within a range of 380 nm to 780 nm. Brightreflective and transmissive color displays are thereby achieved.

In another embodiment of the third liquid crystal device in accordancewith the present invention, the device further includes a diffuser onanother face of the first substrate, on the opposite side of the liquidcrystal layer.

According to this embodiment, the diffuser makes the mirror face of thereflective electrode look as a diffusing face (white surface). Diffusionby the diffuser enables display from a wide view angle. The diffuser maybe disposed at any position above the face of the first substrate, onthe opposite side of the liquid crystal layer. Preferably, the diffuseris disposed between the polarizer and the first substrate inconsideration of the effect of back scattering (scattering of externallight towards the incident side of it). The back scattering notcontributing to the display of the liquid crystal device causes adecreased contrast in a reflective display mode. When the diffuser isdisposed between the polarizer and the first substrate, the polarizercan reduce the quantity of light of back scattering to approximatelyone-half.

In another embodiment of the third liquid crystal device in accordancewith the present invention, the reflective electrode has irregularities.

According to this embodiment, the irregularities eliminate the mirroringon the face of the reflective electrode and render the mirror face intoa diffusing face (white face). Diffusion by the irregularities enablesdisplay with a wide view angle. The irregularities may be formed byforming a photosensitive acrylic resin layer under the reflectiveelectrode, or by roughening the underlying glass substrate with aqueoushydrogen fluoride. It is preferable in order to achieve satisfactoryalignment of the liquid crystals that a transparent planarization filmbe formed on the irregular surface of the reflective electrode so thatthe surface facing the liquid crystal layer (the surface on which analignment film is formed) is planarized.

In another embodiment of the third liquid crystal device in accordancewith the present invention, the reflective electrode is a composite of areflective layer and a transparent electrode layer.

According to this embodiment, the reflective layer of the transflectiveelectrode reflects external light, and the transparent electrode layerapplies a driving voltage to the liquid crystal even if the reflectiveelectrode is not composed of a reflective and conductive single film.

The above-mentioned object of the present invention is also achieved bya third electronic apparatus provided with the third liquid crystaldevice.

The third electronic apparatus in accordance with the present inventionuses a transflective liquid crystal device or a color transflectiveliquid crystal device without double imaging and blurred imaging due toparallax, and can change a display mode between a reflective mode and atransmissive mode. Thus, the electronic apparatus can displayhigh-quality images in any lighted or dark environment regardless of thelevel of ambient or external light.

The object of the present invention is also achieved by a fourth liquidcrystal device including (i) a transflective liquid crystal panelcomprising a pair of first and second transparent substrates; a liquidcrystal layer disposed between the first and second substrates; atransparent electrode formed on a face of the first substrate facing theliquid crystal layer; a reflective electrode formed on a face of thesecond substrate facing the liquid crystal layer; and an illuminationunit provided on an another face of the second substrate, on theopposite side of the liquid crystal layer; and (ii) a driving means fordriving the transparent electrode and the reflective electrode; whereinthe liquid crystal panel is in a dim or black state when not driven.

According to the fourth liquid crystal device of the present invention,the reflective electrode reflects external light incident on the firstsubstrate towards the liquid crystal layer in a reflective display mode.Since the reflective electrode is provided on the face of the secondsubstrate facing the liquid crystal layer, no gap is substantiallyformed between the liquid crystal layer and the reflective electrode.Thus, double imaging and blurred imaging due to parallax do not occur.On the other hand, the reflective electrode comprising a transflectivelayer transmits light which emerges from the illumination unit and isincident on the second substrate towards the liquid crystal layer in atransmissive display mode. Thus, light from the light source achievesbright display in a dark environment. The transflective layer may be areflective film having oblong slits or square fine openings so thatlight partly passes through the film, as in the above-mentioned firstliquid crystal of the present invention, a thin metal transflective filmhaving fine defects, such as pinhole defects or dimples, or a film whichshows overall transflective characteristics. Alternatively, the layermay be composed of a plurality of stripes or island reflectiveelectrodes formed with a predetermined gap.

In the fourth liquid crystal device, the liquid crystal panel drivenbetween the transparent electrode and the reflective electrode by adriving means is a dim state when not driven. That is, it is driven by anormally black mode. Thus, optical leakage from boundaries betweennon-driven liquid crystal pixels or dots can be reduced in atransmissive display mode, resulting in transmissive display having ahigh contrast. Furthermore, undesirable reflection at boundaries betweenpixels or dots can be reduced in a reflective display mode, resulting ina display having a high contrast. Accordingly, an improved contrast isachieved in both a transmissive display mode and a reflective displaymode without covering the gap between the reflective electrodes with ashading film (called a “black matrix” or a “black mask”). Since noshading film is provided, brightness does not decrease in a reflectivedisplay mode.

The fourth liquid crystal device can be driven by various conventionaldriving system, such as a passive matrix driving system, a TFT activematrix driving system, a TFD active matrix driving system, or a segmentdriving system.

In another embodiment of the fourth liquid crystal device in accordancewith the present invention, the device further includes a firstpolarizer provided on another face of the first substrate, on theopposite side of the liquid crystal layer, and at least one firstretardation film disposed between the first substrate and the firstpolarizer.

According to this embodiment, the first polarizer primarily achievessatisfactory display control in both the reflective and transmissivedisplay modes, and the first retardation film primarily reduces effectson tonality, such as coloring, due to the wavelength dispersion oflight.

In another embodiment of the fourth liquid crystal device in accordancewith the present invention, the device further includes a secondpolarizer disposed between the second substrate and the illuminationunit, and at least a second retardation film disposed between the secondsubstrate and the second polarizer.

According to this embodiment, the second polarizer primarily achievessatisfactory display control in the transmissive display mode, and thesecond retardation film primarily reduces effects on tonality, such ascoloring, due to the wavelength dispersion of light.

In another embodiment of the fourth liquid crystal device in accordancewith the present invention, the reflective electrode contains 95% byweight or more of aluminum and has a thickness of 10 nm to 40 nm.

According to this embodiment, a thin transflective type reflectiveelectrode is formed. According to experiments, the transflective typereflective electrode has a transmittance of 1% to 40% and a reflectance50% to 95% within the above thickness range.

In another embodiment of the fourth liquid crystal device in accordancewith the present invention, the device further includes a color filterprovided between the reflective electrode and the first substrate.

According to this embodiment, reflective color display by external lightand transmissive color display using an illumination unit are available.Preferably, the color filter has a transmittance of 25% or more forlight of any wavelength within a range of 380 nm to 780 nm. Brightreflective and transmissive color display is thereby achieved.

In another embodiment of the fourth liquid crystal device in accordancewith the present invention, the device further includes a diffuser onanother face of the first substrate, on the opposite side of the liquidcrystal layer.

According to this embodiment, the diffuser makes the mirror face of thereflective electrode a diffusing face (white surface). Diffusion by thediffuser enables display with a wide view angle. The diffuser may bedisposed at any position above the face of the first substrate, on theopposite side of the liquid crystal layer. Preferably, the diffuser isdisposed between the polarizer and the first substrate in considerationof the effect of back scattering (scattering of external light towardsthe incident side of it). The back scattering not contributing to thedisplay of the liquid crystal device causes a decreased contrast in areflective display mode. When it is disposed between the polarizer andthe first substrate, the polarizer can reduce the quantity of light ofback scattering to approximately one-half.

In another embodiment of the fourth liquid crystal device in accordancewith the present invention, the reflective electrode has irregularities.

According to this embodiment, the irregularities eliminate the mirroringon the face of the reflective electrode and render the mirror face intoa diffusing face (white face). Diffusion by the irregularities enablesdisplay with a wide view angle. The irregularities may be formed byforming a photosensitive acrylic resin layer under the reflectiveelectrode, or by roughening the underlying glass substrate with aqueoushydrogen fluoride. It is preferable in order to achieve satisfactoryalignment of the liquid crystals that a transparent planarization filmbe formed on the irregular surface of the reflective electrode so thatthe surface facing to the liquid crystal layer (the surface on which analignment film is formed) is planarized.

In another embodiment of the fourth liquid crystal device in accordancewith the present invention, the reflective electrode is a composite of areflective layer and a transparent electrode layer.

According to this embodiment, the reflective layer of the transflectiveelectrode reflects external light, and the transparent electrode layerapplies a driving voltage to the liquid crystal even if the reflectiveelectrode is not composed of a reflective and conductive single film.

The above-mentioned object of the present invention is also achieved bya fourth electronic apparatus provided with the fourth liquid crystaldevice.

The fourth electronic apparatus in accordance with the present inventionuses a transflective liquid crystal device or a color transflectiveliquid crystal device without double imaging and blurred imaging due toparallax, and can change a display mode between a reflective mode and atransmissive mode. Thus, the electronic apparatus can displayhigh-quality images in any lighted or dark environment regardless of thelevel of ambient or external light.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a is a longitudinal cross-sectional view of an outline structurein a first embodiment and a second embodiment of a liquid crystal devicein accordance with the present invention.

FIG. 1 b is a plan view of an outline structure in the first embodimentand the second embodiment.

FIG. 2 includes a schematic illustration of the relationship among apolarizer, a retardation film, and a rubbing direction of a liquidcrystal cell, and a characteristic graph between the driving voltage andthe reflectance R/transmittance T in the liquid crystal device.

FIG. 3 is an enlarged cross-sectional view of an outline structure of asecond transparent substrate in a third embodiment of a liquid crystaldevice in accordance with the present invention.

FIG. 4 is a longitudinal cross-sectional view of an outline structure ina fourth embodiment of a liquid crystal device in accordance with thepresent invention.

FIG. 5 a is a longitudinal cross-sectional view of an outline structurein a fifth embodiment of a liquid crystal device in accordance with thepresent invention.

FIG. 5 b is a plan view of an outline structure in a fifth embodiment ofa liquid crystal device in accordance with the present invention.

FIG. 6 is a plan view of a reflective electrode provided with slits in asixth embodiment of a liquid crystal device in accordance with thepresent invention.

FIG. 7 is a plan view of another reflective electrode provided withslits in the sixth embodiment.

FIG. 8 is a plan view of still another reflective electrode providedwith slits in the sixth embodiment.

FIG. 9 is a plan view of a further reflective electrode provided withslits in the sixth embodiment.

FIG. 10 is a plan view of a still further reflective electrode providedwith slits in the sixth embodiment.

FIG. 11 is a plan view of another reflective electrode provided withslits in the sixth embodiment.

FIG. 12 is a plan view of still another reflective electrode providedwith slits in the sixth embodiment.

FIG. 13 is a conceptual view for illustrating the alignment direction ofa liquid crystal in the center between substrates in a seventhembodiment and a ninth embodiment in accordance with the presentinvention.

FIG. 14 is a longitudinal cross-sectional view of an outline liquidcrystal device in an eighth embodiment in accordance with the presentinvention.

FIG. 15 is a plan view of a reflective electrode structure in the eighthembodiment.

FIG. 16 is a plan view of another reflective electrode structure in theeighth embodiment.

FIG. 17 is a plan view of still another reflective electrode structurein the eighth embodiment.

FIG. 18 is a plan view of a further reflective electrode structure inthe eighth embodiment.

FIG. 19 is a table showing contrasts in a reflective display mode and atransmissive display mode when the angle φ is varied in a ninthembodiment in accordance with the present invention.

FIG. 20 is a table showing contrasts in a reflective display mode and atransmissive display mode when the angle ψ is varied in the ninthembodiment.

FIG. 21 a is a schematic plan view of a TFD driving element and a pixelelectrode in a tenth embodiment in accordance with the presentinvention.

FIG. 21 b is a cross-sectional view taken along line B-B′ in FIG. 21 a.

FIG. 22 is an equivalent circuit diagram of a liquid crystal device anda driving circuit in the tenth embodiment.

FIG. 23 is a partially broken isometric view for schematically showingthe liquid crystal device in the tenth embodiment.

FIG. 24 is an equivalent circuit diagram of various elements and leadlines in a plurality of pixels formed in a matrix which constitutes animage display region in a liquid crystal device in an eleventhembodiment in accordance with the present invention.

FIG. 25 is a plan view of a plurality of adjacent pixels on atransparent substrate provided with data lines, scanning lines and pixelelectrodes in the eleventh embodiment.

FIG. 26 is a cross-sectional view taken along line C-C′ in FIG. 25.

FIG. 27 is a graph showing transmittance of individual color layers in acolor filter in the first or fifth embodiment.

FIG. 28 includes outline isometric views of various electronicapparatuses in a twelfth embodiment in accordance with the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

A best mode in each embodiment for carrying out the present inventionwill now be described with reference to the drawings.

A first embodiment of a liquid crystal device in accordance with thepresent invention will be described with reference to FIGS. 1 a and 1 b.FIG. 1 a is a longitudinal cross-sectional view of an outline structurein the first embodiment of the present invention. FIG. 1 b is an outlineplan view of the first embodiment shown in FIG. 1 a. In FIG. 1 b, acolor filter and a black matrix layer shown in FIG. 1 a are omitted sothat the electrode arrangement is readily visible, and only threevertical and three horizontal stripe electrodes are depicted, althoughmany stripe electrodes are provided in an actual liquid crystal device.Although the first embodiment fundamentally relates to a passive matrixliquid crystal device, it is also applicable to an active matrix device,a segment-type device, and other types of liquid crystal devices.

As shown in FIGS. 1 a and 1 b, in the first embodiment, a liquid crystalcell is formed in which a liquid crystal layer 3 is disposed between twotransparent substrates 1 and 2 and sealed by a sealing frame 4. Theliquid crystal layer 3 is composed of a nematic liquid crystal having apredetermined twist angle. A color filter 5 is formed on an innersurface of the front transparent substrate 1, and the color filter 5 isprovided with three red (R), green (G), and blue (B) coloring layerswhich are arranged in a predetermined pattern. The surface of the colorfilter 5 is covered with a transparent protective film 10, and aplurality of stripe transparent electrodes 6 composed of, for example,indium tin oxide (ITO) is formed on the surface of the protective film10. An alignment film 9 is formed on the transparent electrodes 6, andis previously subjected to rubbing treatment in a predetermineddirection.

A plurality of stripe reflective electrodes 7, which is formedcorresponding to coloring layers of the color filter 5, is arranged onthe inner face of the rear transparent substrate 2 so as to cross thetransparent electrodes 6. In an active matrix device provided with TFDelements and TFT elements, each reflective electrode 7 is rectangular,and is connected to a lead line through an active element. Thereflective electrode 7 is composed of chromium or aluminum, and has areflective surface which reflects light incident on the transparentsubstrate 1. An alignment film 19 is formed on the reflective electrode7 as described above. Each reflective electrode 7 has many openings 7 bhaving a diameter of 2 μm (see FIG. 1 b), and the openings 7 b have atotal area corresponding to approximately 10% of the total area of thereflective electrode 7.

A polarizer 11 is disposed above the outer face of the front transparentsubstrate 1, and a retardation film 13 is disposed between the polarizer11 and the transparent electrode 1. At the rear side of the liquidcrystal cell, a retardation film 14 is provided behind the transparentsubstrate 2, and a polarizer 12 is provided behind the retardation film14. A backlight 15 provided with a fluorescent tube 15 a emitting whitelight and a light guide plate 15 b having an incident end face along thefluorescent tube 15 a is arranged behind the polarizer 12. The lightguide plate 15 b is composed of a transparent body, such as an acrylicresin plate, having an entire rough surface for scattering or a printedlayer for scattering. It receives light from the fluorescent tube 15 aas a light source at the end face, and emerges substantially uniformlight from the top face in the drawing. Examples of other usablebacklights include a light emitting diode (LED) and anelectroluminescent (EL) lamp.

In the first embodiment, a black matrix layer 5 a as a shading layer isformed between two coloring layers of the color filter 5 in such mannerthat the black matrix layer 5 a is provided substantially correspondingto the region 7 a, when viewing from the top, between two reflectiveelectrodes 7, so that the black matrix layer prevents optical leakagefrom the region 7 a in a transmissive display mode. The black matrixlayer 5 a is formed of a coated chromium layer or a photosensitive blackresin layer.

The operation of the first embodiment having the above structure willnow be described.

First, a reflective display mode will be described. External light, inFIG. 1, transmitted through the polarizer 11, the retardation film 13,the color filter 5, and then passing through the liquid crystal layer 3,is reflected by each reflective electrode 7, and emerges again from thepolarizer 11. The polarizer 11 is controlled to a transmissive state(lighted state), an absorbed state (dim state), or an intermediatebrightness state therebetween in response to a voltage applied to theliquid crystal layer 3.

Next, a transmissive display mode will be described. Light from thebacklight 15 is converted to a predetermined polarized light beam by thepolarizer 12 and the retardation film 14, enters the liquid crystallayer 3 through openings 7 b of each reflective electrode 7, passesthough the liquid crystal layer 3, and then is transmitted through thecolor filter 5 and the retardation film 13. Brightness of the polarizer11 is controlled to a transmissive state (lighted state), an absorbedstate (dim state), or an intermediate state therebetween in response toa voltage applied to the liquid crystal layer 3.

This embodiment can provide a color liquid crystal device without doubleimaging and blurred imaging, and which can change a display mode betweena reflective mode and a transmissive mode.

In the first embodiment, the polarizer 11 as a first polarizer, theretardation film 13 as a first retardation film, the polarizer 12 as asecond polarizer, and the retardation film 14 as a second retardationfilm, are provided; hence, the polarizers 11 and 12 can satisfactorilycontrol display in both the reflective display mode and the transmissivedisplay mode. The retardation film 13 moderates effects on tonality suchas coloring due to wavelength dispersion of light in the reflectivedisplay mode (the retardation film 13 optimizes display in thereflective mode). Also, the retardation film 14 moderates effects ontonality such as coloring due to wavelength dispersion of light in thetransmissive display mode (the retardation film 14 optimizes display inthe transmissive mode, under the condition of the optimization by theretardation film 13 in the reflective display mode). Although oneretardation film is used in this embodiment regarding each of theretardation film 13 and the retardation film 14, a plurality ofretardation films may be provided at positions for correcting coloringof the liquid crystal cell and for correcting the view angle. Use of aplurality of retardation films further facilitates optimization ofcorrection of the coloring and the view angle.

The openings 7 b provided in each reflective electrode 7 in the firstembodiment are composed of square fine openings or oblong slits whichare regularly arranged in the plane of the reflective electrode 7, orcomposed of fine defects, such as pinholes and dimples, dotted in thereflective electrode 7. These openings transmit light. The structure ofsuch openings 7 b will be described in subsequent sixth to eighthembodiments in detail with reference to FIGS. 7 to 11, and thus detaileddescription is omitted in this embodiment.

Transmissive display is performed by light emerging from the backlight15 through the openings 7 b provided in the reflective electrode 7 inthe first embodiment. Also, in a structure for performing transmissivedisplay in which light is introduced through openings 7 a in thereflective electrode 7 (see the thirteenth embodiment described below),a combination of a polarizer 11 with a retardation film 13 and acombination of a polarizer 12 and a retardation film 14 can providesatisfactory display in a reflective display mode and a transmissivedisplay mode, respectively, and can moderate coloring due to wavelengthdispersion of light.

A second embodiment of a liquid crystal device in accordance with thepresent invention will now be described with reference to FIGS. 1 a and1 b. The fundamental structure in the second embodiment is the same asthat in the first embodiment. In the second embodiment, materials forand properties of the liquid crystal, the reflective electrode, thealignment film, and the polarizer are specifically limited. Although thesecond embodiment fundamentally relates to a passive matrix liquidcrystal display device, it is also applicable to an active matrixdevice, a segment-type device, and other types of liquid crystaldevices.

With reference to FIGS. 1 a and 1 b, in the second embodiment, rubbingtreatment in a predetermined direction is performed on the alignmentfilm 9 formed on the transparent electrode 6 so that liquid crystalmolecules in the liquid crystal layer 3 have a pretilted angle ofapproximately 85 degrees in the rubbing direction. The above-describedalignment film 19 is formed on the reflective electrode 7, but is notsubjected to rubbing treatment. As the reflective electrode 7, a metalfilm with a thickness of 25 nm is used in which aluminum containing 1.0percent by weight of neodymium is sputtered. The aluminum used has apurity of 95 percent by weight, and the thickness is set to be in arange of 10 nm to 40 nm. Such a reflective electrode 7 may also be usedin the first embodiment. Quarter-wavelength plates are used asretardation films 13 and 14.

In the second embodiment, the polarization axes P1 and P2 of thepolarizers 11 and 12 are set in the same direction, as shown in FIG. 2(a). The slow axes C1 and C2 of the retardation films 13 and 14 (thequarter-wavelength plates) are set in the direction rotating clockwiseby θ=45 degrees from the polarization axes P1 and P2 of the polarizers11 and 12, respectively. The rubbing direction R1 of the alignment film9 on the inner face of the transparent substrate 1 also agrees with theslow axes C1 and C2 of the retardation films 13 and 14 (thequarter-wavelength plates). The rubbing direction R1 determines thetilted direction of the liquid crystal layer 3 when a voltage isapplied. A nematic liquid crystal having negative 2 is used as theliquid crystal layer 3.

FIG. 2( b) shows a driving voltage versus a reflectance R relationshipin a reflective display mode and a driving voltage versus atransmittance T relationship in a transmissive display mode in thesecond embodiment. The display state when no voltage is applied is dimor black. That is, the liquid crystal device is driven by a normallyblack mode. Since such a driving mode suppresses optical leakage andunnecessarily reflected light from a gap 7 a between reflectiveelectrodes 7 with respect to a non-driven liquid crystal, formation of ablack matrix layer 5 a is unnecessary.

The operation of the second embodiment having the above structure willnow be described.

First, a reflective display mode will be described. External light, inFIG. 1, is transmitted through the polarizer 11, the retardation film13, and the color filter 5, then passing through the liquid crystallayer 3, and is reflected by each reflective electrode 7, and stillfurther emerges from the polarizer 11. Brightness of the polarizer 11 iscontrolled to a transmissive state (lighted state), an absorbed state(dim state), or an intermediate state therebetween in response to avoltage applied to the liquid crystal layer 3.

Next, a transmissive display mode will be described. Light from thebacklight 15 is converted into a predetermined polarized light beam bythe polarizer 12 and the retardation film 14 (circularly polarizedlight, elliptically polarized light, or linearly polarized light),enters the liquid crystal layer 3 through openings 7 b of eachreflective electrode 7, and passes though the liquid crystal layer 3,then is transmitted through the color filter 5 and the retardation film13, respectively. Brightness of the polarizer 11 is controlled to atransmissive state (lighted state), an absorbed state (dim state), or anintermediate state therebetween in response to a voltage applied to theliquid crystal layer 3.

This embodiment can provide a color liquid crystal device without doubleimaging and blurred imaging, and which can change a display mode betweena reflective mode and a transmissive mode.

A third embodiment of a liquid crystal device in accordance with thepresent invention will now be described with reference to FIG. 3. FIG. 3is an enlarged cross-sectional view of a structure on the inner face ofa transparent substrate in the third embodiment.

In the third embodiment, as shown in FIG. 3, a reflective electrode 17is provided in place of the reflective electrode 7 in the firstembodiment, and other structures are the same as those in the firstembodiment. Although the third embodiment fundamentally relates to apassive matrix liquid crystal device, it is also applicable to an activematrix device, a segment-type device, and other types of liquid crystaldevices.

In the third embodiment, the reflective electrode 17 is provided withirregularities having a height of, for example, approximately 0.8 μm.The irregularities remove the mirror face of the reflective electrode 17and impart a scattering face (a white face) thereto. Scattering causedby the irregularities permits display with a wider view angle.

A method for making the reflective electrode 17 will now be described.

A photosensitive resist for the reflective electrode 17 is applied tothe inner face of the transparent substrate 2 shown in FIG. 1 by spincoating or the like, and is exposed to light in which the amount of thelight is adjusted by a mask having fine openings. The photosensitiveresist is fired, if necessary, and is developed. Portions correspondingto the openings of the mask are selectively removed by the developmentto form a supporting layer 16 having a wavy cross-sectional shape asshown in the drawing. A wavy cross-sectional shape as in the supportinglayer 16 shown in the drawing may be formed by selective removing orremaining at the portions corresponding to the openings of the mask bythe photolithographic process, and then by smoothing the irregular shapeby etching or heating. Alternatively, another layer may be deposited onthe surface of the formed supporting layer to smooth the surface.

Next, a metallic thin film is vapor-deposited on the surface of thesupporting layer 16 by sputtering or the like to form a reflectiveelectrode 17 with a reflective surface. Examples of metals used includeAl, CrAg, and Au. Since the shape of the reflective electrode 17reflects the wavy surface shape of the supporting layer 16, its overallsurface has irregularities. A planarization film 18 composed of atransparent resin may be formed thereon, if necessary, and then analignment film 19 is formed thereon.

Such provision of the reflective electrode 17 can prevent directreflection of external light in a reflective display mode, and improvedvisibility is achieved without diminished display brightness.

In this case, a reflective layer having the same shape as that of thereflective electrode 17 may be formed and then a transparent electrodemay be formed thereon. When the reflective electrode consists of acomposite of the reflective layer and the transparent electrode layer sothat the reflective layer reflects external light, and the transparentelectrode layer applies a liquid crystal driving voltage, the reflectiveelectrode having irregularities functions as a transflective layer.

A fourth embodiment of a liquid crystal device in accordance with thepresent invention will now be described with reference to FIG. 4. FIG. 4is a longitudinal cross-sectional view of an outline structure in thefourth embodiment in accordance with the present invention. In FIG. 4,the same elements as in the first embodiment shown in FIG. 1 a arereferred to by the same reference numerals, without further description.

As shown in FIG. 4, in the fourth embodiment, a transmissive opticaldiffuser 21 is disposed between the retardation film 13 and thetransparent substrate 1, in addition to the structure shown in the firstembodiment. The optical diffuser 21 may be of an internal diffusion typein which transparent particles are dispersed in a transparent substratesuch as an acrylic resin having a different refractive index, or of asurface diffusion type in which the surface of a transparent substrateis roughened (to form a mat). The other structures are the same as thosein the first embodiment.

The optical diffuser 21 can also prevent direct reflection of externallight on the reflective electrode 7 in a reflective display mode,resulting in improved visibility. The position of the optical diffuser21 is not limited to that shown in FIG. 4, as long as it is disposedforward the reflective layer. For example, the optical diffuser may beformed on the reflective electrode or the reflective layer.

A fifth embodiment of a liquid crystal device in accordance with thepresent invention will now be described with reference to FIGS. 5 a and5 b. FIG. 5 a is a longitudinal cross-sectional view of an outlinestructure in a fifth embodiment in accordance with the presentinvention, and FIG. 5 b is an outline plan view in the fifth embodiment.In FIG. 5 b, a color filter and a black matrix layer shown in FIG. 5 aare not depicted to facilitate a view of an electrode arrangement, andonly three vertical stripe electrodes and three horizontal stripeelectrodes are indicated for simplicity. An actual liquid crystal devicehas many more stripe electrodes. In FIGS. 5 a and 5 b, the same elementsas in the first embodiment shown in FIGS. 1 a and 1 b are referred to bythe same reference numerals, without further description. Although thefifth embodiment fundamentally relates to a passive matrix liquidcrystal device, it is also applicable to an active matrix device, asegment-type device, and other types of liquid crystal devices.

As shown in FIGS. 5 a and 5 b, in the fifth embodiment, reflectiveelectrodes 17′ each having many fine pores 17′a are provided in place ofthe reflective electrodes 7 in the first embodiment, and the otherstructures are the same. Light from the backlight 15 passes through finepores 17′a of the reflective electrodes 17′ in a transmissive displaymode so that display on the liquid crystal is visible. After thereflective electrodes 17′ are formed by vapor evaporation or sputtering,a resist layer having openings is formed by photolithography, and thenthe fine pores 17′a are formed by etching.

In the fifth embodiment, the fine pores 17′a ensure bright display in atransmissive display mode, and prevents reflection of external light ina reflective display mode as in the third embodiment.

Sixth Embodiment

A sixth embodiment of a liquid crystal device in accordance with thepresent invention will now be described with reference to FIGS. 6 and12. The fundamental structure in the sixth embodiment is the same asthat in the first embodiment, but the structure relating to thereflective electrode 7 in the first embodiment is specified in the sixthembodiment. FIGS. 6 to 12 are plan views of reflective electrodesprovided with various slits. Although the sixth embodiment fundamentallyrelates to a passive matrix liquid crystal device, it is also applicableto an active matrix device, a segment-type device, and other types ofliquid crystal devices.

In the sixth embodiment shown in FIG. 6, a plurality of transparentelectrodes 801 functioning as scanning lines are formed on the innersurface of the transparent substrate 1 (see FIG. 1) in a stripedpattern, in which the transparent electrode 801 is an example of thetransparent electrode 6. Reflective electrodes 802 as data lines areformed on the inner surface of the transparent substrate 2 (see FIG. 1),in which the reflective electrode 802 is an example of the reflectiveelectrode 7. Each reflective electrode (data line) 802 is provided withslits 803 as an example of the openings 7 b. Each reflective electrode802 allotted to any one of red (R), green (G), and blue (B) forms onedot at a region overlapping one transparent electrode 801, and adjacentthree R, G and B dots constitute one substantially square pixel. In eachdot, each reflective electrode 802 has four slits 803.

Since each reflective electrode 802 has oblong slits 803 in the sixthembodiment, an oblique electric field caused by a short side 803 a ofeach slit 803 (the in-substrate component is parallel to thelongitudinal direction of the slit 803) is moderated depending thelength of the long side 803 b of the slit 803. That is, an obliqueelectric field caused by the long side 803 b of the slit 803 (thein-substrate component is perpendicular to the longitudinal direction ofthe slit 803) controls movement of liquid crystal molecules in thevicinity of the slit. Thus, such a structure can suppress insufficientalignment of the liquid crystal which is caused by disagreement betweenthe oblique electric field due to the short side 803 a and the obliqueelectric field due to the long side 803 b of the slit 803, and thus cansuppress overall insufficient alignment of the liquid crystal caused bythe oblique electric fields by the slit 803. Also, the oblique electricfield due to the long side 803 b can be voluntarily used for driving theliquid crystal.

In accordance with the sixth embodiment, display defects can be reduced,and electrical power consumed by the liquid crystal device can besimultaneously reduced by a reduced threshold voltage when the liquidcrystal is driven. When a countermeasure is taken only for the obliqueelectric field due to the long side 803 b of the slit 803, and noconsideration is given to the oblique electric field due to the shortside 803 a of the slit 803, overall insufficient alignment of the liquidcrystal caused by the oblique electric field can be reduced.Alternatively, voluntary use of the oblique electric field due to thelong side 803 b of the slit 803 facilitates overall effective use of theoblique electric field due to the slit 803.

Such oblong slits 803 can be readily formed by a photostep using aresist, a development step, and then a peeling step. Thus, the slits 803can be simultaneously formed when the reflective electrodes 802 areformed. The width of each slit 803 is in a range of preferably 0.01 μmto 20 μm, and more preferably 4 μm or more. Since a viewer cannotrecognize such a structure, a reflective display mode and a transmissivedisplay mode can be simultaneously achieved without deterioration ofimage quality due to the slit 803. Preferably, the slit 803 has an arearatio of 5% to 30% with respect to the reflective electrode 802. Such aratio can moderate decreased brightness in a reflective display mode,and achieves a transmissive display mode by light incident on the liquidcrystal layer via the slits 803 of the reflective electrodes 802.

In the sixth embodiment, a plurality of stripe reflective electrodes 802is formed at a predetermined gap, and slits 803 extend in thelongitudinal direction of the reflective electrodes 802 (thelongitudinal direction in FIG. 6). Thus, a countermeasure for theoblique electric field caused by the slits 803 is effective for theoblique electric field caused by gaps 802 b between the reflectiveelectrodes 802. Furthermore, the reflective electrodes 802 and the slits803 can be simultaneously formed; hence, the design of the mask used inthe formation can be simplified. That is, a photomask for forming thereflective electrodes 802 may include a pattern for the slits 803,without providing an additional step for forming the slits 803.

In the sixth embodiment, each slit 803 extends to a position facing agap 801 b between the transparent electrodes 801. Thus, edges of eachreflective electrode 802, which define short sides 803 a of each slit803 and are opposingly disposed at a relatively large distance, lie in agap 801 b between transparent electrodes 801. Namely, since the edge isdistant from a region in which a voltage is applied between thetransparent electrode 801 and the reflective electrode 802, the effectof the oblique electric field due to the short side 803 a of the slit803 causing insufficient alignment of the liquid crystal can besignificantly and effectively reduced.

As a modification of the sixth embodiment, in consideration of this, asshown in FIG. 7, the slit 803 may extend over a plurality of pixels ormay extend towards the exterior of the image display region. In such astructure, each pixel does not have or the image display area does notinclude the edges of reflective electrodes 802 defining short sides 803(as not shown in FIG. 7) of slits 803 opposingly disposed at arelatively large distance; hence, the effect of the oblique electricfield due to the short side 803 a of the slit 803 causing insufficientalignment of the liquid crystal can be significantly and effectivelyreduced.

Possible further modifications of the oblong slit 803 in the sixthembodiment include two slits 803 for one dot as shown in FIG. 8; twoslits 703 for one dot, each slit having a long side in the directionperpendicular to the reflective electrode 702 (parallel to thetransparent electrode 701) as shown in FIG. 9; one slit 903 for one dot,each slit having a long side in the direction slant to the reflectiveelectrode 902 (slant to the transparent electrode 901) as shown in FIG.10; and a slit 1003 consisting of a plurality of oblong slit elementshaving long sides in directions parallel to and perpendicular to thereflective electrode 1002 (parallel to and perpendicular to thetransparent electrode 1001) as shown in FIG. 11.

In the sixth embodiment, as shown in FIG. 12, a width of a slit 1202provided in a reflective electrode 1201 may be substantially equal to agap (an interdot region) 1203 between two reflective electrodes 1201.When L1 is nearly equal to L2, wherein L1 is the width of the gap 1203and L2 is the width of the slit 1020, a photomask does not require highdesign accuracy and thus can be readily designed. Furthermore, provisionof such slits causes slightly increased cost.

As in the second to fourth embodiments, the sixth embodiment can includenormally black mode driving, provision of a diffuser, or a reflectiveelectrode with irregularities. In the normally black mode driving, theblack matrix layer 5 a may be omitted.

Seventh Embodiment

A seventh embodiment of a liquid crystal device in accordance with thepresent invention will now be described with reference to FIGS. 13 and 6to 10.

In the seventh embodiment, attention is paid to the alignment directionof the liquid crystal molecules in the center of the liquid crystallayer disposed between the two transparent substrates in a liquidcrystal device which is similar to that in the sixth embodiment.

FIG. 13 is a longitudinal cross-sectional view for illustrating thealignment direction of a liquid crystal in the center between thesubstrates. A liquid crystal 503 is in a predetermined twist-alignmentstate between two substrates 501 and 502. The long axis direction of aliquid crystal molecule 504 lying substantially in the center betweenthe substrates is defined as an alignment direction 505.

In the seventh embodiment, with reference to FIG. 6 described above, apotential difference generated between a reflective electrode (dataline) 802 and a transparent electrode (scanning line) 801 forms anoblique electric field which drives a liquid crystal on an oblong slit803 to achieve transmissive display. As shown in FIG. 6, an anglebetween the longitudinal direction of the slit 803 of the reflectiveelectrode 802 (the y direction in FIG. 6) and the alignment direction804 of the liquid crystal molecule in the center between the substratesis defined as ξ. Display defects (disclination) due to a reverse tiltdomain occur in a range of −90°≦ξ≦−60° or 60°≦ξ≦90°, and thus bright,high-quality transmissive display is not achieved. A possible reason isformation of a tilt domain by orthogonal crossing of the alignmentdirection of the liquid crystal molecule in the center between thesubstrates and the longitudinal direction of the reflective electrode.The display defects formed in the region causes an inevitable increasein the threshold voltage during driving of the liquid crystal. Displaydefects such as disclination due to the reverse tilt domain areavoidable in a range of −60°≦ξ≦60°, and thus bright, high-qualitytransmissive display is achieved. Since the display defects barelyoccur, the threshold voltage during driving of the liquid crystal can bereduced, resulting in reduced power consumption of the liquid crystaldevice. The above advantage is particularly noticeable in a range of−30°≦ξ≦30°.

In cases of oblong slits 803 shown as modifications of the sixthembodiment in FIGS. 7 and 8, the longitudinal direction is parallel tothe reflective electrode 802 as in FIG. 6, and bright, high-qualitytransmissive display is achieved in a range of −60°≦ξ≦60°. The aboveadvantage is particularly noticeable in a range of −30°≦ξ≦30°.

Also, in the slits 703 and 903, as modifications of the sixthembodiment, shown in FIGS. 9 and 10, an angle between the longitudinaldirection of the slit 703 of the reflective electrode 702 (the Xdirection in the drawings) and the alignment direction 704 of the liquidcrystal molecule in the center between the substrates is defined as ξ,and an angle between the longitudinal direction 904 of the slit 903 ofthe reflective electrode 902 and the alignment direction 905 of theliquid crystal molecule in the center between the substrates is definedas ξ. A preferable angle is in a range of −60°≦ξ≦60°. The aboveadvantage is particularly noticeable in a range of −30°≦ξ≦30°.

The effects of the present invention described in the seventh embodimentcan be further ensured by specifying the alignment direction 506 of theliquid crystal molecule in the vicinity of the substrate 502 in FIG. 13.That is, in FIG. 6, an angle between the alignment direction 805 of theliquid crystal molecule in the vicinity of the lower substrate and thelongitudinal direction (the Y direction in FIG. 6) of the slit 703 isdefined as δ. A preferable angle is in a range of −30°≦δ≦30°. In a rangeoutside −30°≦δ≦30°, the liquid crystal molecule at the substrateinterface is reverse-titled by the effect of the oblique electric fieldto cause display defects. Limitation of the angle in a range of−30°≦δ≦30° can reduce the threshold voltage during driving of the liquidcrystal, resulting in reduced power consumption of the liquid crystaldevice. The above advantage is particularly noticeable in a range of−10°≦δ≦10°.

Also, in modifications shown in FIGS. 7 to 10, an angle between thealignment direction of the liquid crystal molecule in the vicinity ofthe lower substrate and the longitudinal direction of the slit isdefined as δ. A preferable angle is in a range of −30°≦δ≦30°. Limitationof the angle in a range of −30°≦δ≦30° can reduce the threshold voltageduring driving of the liquid crystal, resulting in reduced powerconsumption of the liquid crystal device. The above advantage isparticularly noticeable in a range of −10°≦δ≦10°.

As in the second to fourth embodiments, the sixth embodiment can includenormally black mode driving, provision of a diffuser, or a reflectiveelectrode with irregularities. In the normally black mode driving, theblack matrix layer 5 a may be omitted.

Eighth Embodiment

An eighth embodiment of a liquid crystal device in accordance with thepresent invention will now be described with reference to FIGS. 14 to18. FIG. 14 is a longitudinal cross-sectional view of an outlinestructure in the eighth embodiment in accordance with the presentinvention. In FIG. 14, the same elements as in the first embodimentshown in FIG. 1 a are referred to by the same reference numerals,without further description. FIGS. 15 to 17 are plan views of concretereflective electrode structures, and FIG. 18 is a plan view of amodification of the reflective electrode.

As shown in FIG. 14, each reflective electrode 107 in the eighthembodiment is one size smaller than each respective transparentelectrode 6, as compared with the first embodiment. In an active matrixdevice provided with TFD elements and TFT elements, the reflectiveelectrode 114 has a rectangular shape, and is connected to a lead linevia an active element. The other structures are the same as those in thefirst embodiment.

In the eighth embodiment, a reflective electrode 107 having a smallerarea than that of a transparent electrode 6 on the inner face of atransparent substrate 1 is formed on the inner face of a transparentsubstrate 2 so that an oblique electric field generated between the twoelectrodes partly drives the liquid crystal layer 3 facing a gap 107 bin which a reflective electrode 107 is not provided (thus, the gaptransmits light from the backlight 15).

The operation of the eighth embodiment having the above structure willnow be described.

First, a reflective display mode will be described. External light, inFIG. 14, is transmitted through a polarizer 11, a retardation film 13, acolor filter 5, and passes the liquid crystal layer 3, and then isreflected by each reflective electrode 107, and emerges from thepolarizer 11. Brightness of the polarizer 11 is controlled to atransmissive state (lighted state), an absorbed state (dim state), or anintermediate state therebetween in response to a voltage applied to theliquid crystal layer 3.

Next, a transmissive display mode will be described. Light from thebacklight 15 is converted into a predetermined polarized light beam by apolarizer 12 and the retardation film 14, enters the liquid crystallayer 3 through each gap 107 b in which a reflective electrode 107 isnot formed, passes though the liquid crystal layer 3, and is transmittedthrough the color filter 5 and the retardation film 13. The liquidcrystal layer 3 is driven by an oblique electric field between thereflective electrode 107 and the transparent electrode 6, havingdifferent sizes, and thus brightness of the polarizer 11 is controlledto a transmissive state (lighted state), an absorbed state (dim state),or an intermediate state therebetween in response to a voltage appliedto the liquid crystal layer 3.

This embodiment can provide a color liquid crystal device without doubleimaging and blurred imaging, and which can change a display mode betweena reflective mode and a transmissive mode.

In the eighth embodiment, actual structures of the transparent electrode6 and the reflective electrode 107 which generate such an obliqueelectric field will be described in FIGS. 15 to 17.

FIG. 15 shows a structure in which the present invention is applied to aTFD active matrix liquid crystal device. Scanning lines 202 are formedon the inner face of a lower substrate, and a TFD element 203 and areflective electrode 204 are formed corresponding to each dot.Transparent electrodes 201 as data lines are formed on the inner face ofan upper substrate. The transparent electrode 201 has a larger area thanthat of the reflective electrode 204 in each pixel, and extends to theopposing region in which the reflective electrode 204 is not formed.When a driving voltage is applied to the liquid crystal, an obliqueelectric field is generated at the gap 205 (an edge of the reflectiveelectrode 204) in which the reflective electrode 204 is not formed, by apotential difference between the reflective electrode 204 and thetransparent electrode 201. The oblique electric field drives the liquidcrystal in the vicinity of the reflective electrode 204, andtransmissive display is achieved.

FIG. 16 is a structure when the present invention is applied to a simpleor passive matrix liquid crystal device. Reflective electrodes 302 asdata lines are formed on the inner face of a lower substrate. Aplurality of transparent electrodes 301 as scanning lines is formed onthe inner face of an upper electrode in a striped pattern. When apotential difference is generated between a reflective electrode 302 anda transparent electrode 301 at a gap 303 between reflective electrodes302 in which the transparent electrode (scanning line) 301 is formed onthe upper substrate, an oblique electric field is formed. The obliqueelectric field drives the liquid crystal facing the gap 303, andtransmissive display is achieved.

FIG. 17 shows a structure when the present invention is applied to a TFTactive matrix liquid crystal device. Gate lines 403 and scanning lines402 are formed on the inner face of a lower substrate, and a TFT element404 and a reflective electrode 405 are formed corresponding to each dot.A transparent electrode 401 as a common electrode (a counter electrode)is formed on the inner face of an upper substrate. The transparentelectrode 401 has a larger area than that of the reflective electrode405 in each pixel, and extends to the opposing region in which thereflective electrode 405 is not formed. Thus, an oblique electric fieldis generated at the gap 406 (an edge of the reflective electrode 405) inwhich the reflective electrode 405 is not formed, by a potentialdifference between the reflective electrode 405 and the transparentelectrode 401. The oblique electric field drives the liquid crystal inthe vicinity of the reflective electrode 405, and transmissive displayis achieved.

As a modification of the eighth embodiment, as shown in FIG. 18,openings 603 may be provided in each reflective electrode 602 andtransparent electrodes 601 may be provided in regions facing theopenings 603. Also, in such a structure, a potential difference betweenthe reflective electrode 602 and the transparent electrode 601 generatesan oblique electric field, and the oblique electric field drives theliquid crystal at the openings 603, and transmissive display isachieved.

As in the second to fourth embodiments, the eighth embodiment caninclude normally black mode driving, provision of a diffuser, or areflective electrode with irregularities. In the normally black modedriving, the black matrix layer 5 a may be omitted.

A ninth embodiment of a liquid crystal device in accordance with thepresent invention will now be described with reference to FIGS. 13 to17.

In the ninth embodiment, attention is paid to the alignment direction ofthe liquid crystal molecules in the center of the liquid crystal layerdisposed between the two transparent substrates in a liquid crystaldevice which is similar to that in the eighth embodiment.

When an electrode arrangement shown in FIG. 15 in the ninth embodimentis employed, an angle between the longitudinal direction of thereflective electrode 204 (the Y direction in FIG. 15) and the alignmentdirection 206 of the liquid crystal molecule in the center between thesubstrates is defined as φ. Display defects (disclination) due to areverse tilt domain occur in a range of −90°≦φ≦−60° or 60°≦φ≦90°, andthus bright, high-quality transmissive display is not achieved. Apossible reason is formation of a tilt domain by orthogonal crossing ofthe alignment direction of the liquid crystal molecule in the centerbetween the substrates and the longitudinal direction of the reflectiveelectrode. The display defects formed in the region causes an inevitableincrease in the threshold voltage during driving of the liquid crystal.

A table shown in FIG. 19 shows a contrast in a reflective display mode(the ratio of a reflectance at a white display mode to a reflectance ata black display mode) and a contrast in a transmissive display mode (theratio of a transmittance at a white display mode to a transmittance at ablack display mode) when the above-defined angle φ is varied. In thiscase, the liquid crystal mode is left-twisted by 255 degrees. As shownin the table in FIG. 19, an angle in a range of −60°≦φ≦60° is essentialfor achieving a contrast of 10 or more which is necessary forhigh-quality image display in a reflective display mode and forsimultaneously achieving a contrast of 5 or more which is necessary forhigh-quality image display in a transmissive display mode. Displaydefects such as disclination due to the reverse tilt domain areavoidable in a range of −60°≦φ≦60°, and thus bright, high-qualitytransmissive display is achieved. Since the display defects barelyoccur, the threshold voltage during driving of the liquid crystal can bereduced, resulting in reduced power consumption of the liquid crystaldevice. The above advantage is particularly noticeable in a range of−30°≦φ≦30°.

When an electrode arrangement shown in FIG. 16 is employed, an anglebetween the longitudinal direction of the reflective electrode 302 (theY direction in FIG. 16) and the alignment direction 304 of the liquidcrystal molecule in the center between the substrates is defined as φ.Display defects (disclination) due to a reverse tilt domain occur in arange of −90°≦φ≦−60° or 60° C.≦φ≦90°, and thus bright, high-qualitytransmissive display is not achieved. A possible reason is formation ofa tilt domain by orthogonal crossing of the alignment direction of theliquid crystal molecule in the center between the substrates and thelongitudinal direction of the reflective electrode. The display defectsformed in the region causes an inevitable increase in the thresholdvoltage during driving of the liquid crystal. Display defects such asdisclination due to the reverse tilt domain are avoidable in a range of−60°≦φ≦60°, and thus bright, high-quality transmissive display isachieved. Since the display defects barely occur, the threshold voltageduring driving of the liquid crystal can be reduced, resulting inreduced power consumption of the liquid crystal device. The aboveadvantage is particularly noticeable in a range of −30°≦φ≦30°.

When an electrode arrangement shown in FIG. 17 is employed, an anglebetween the longitudinal direction of the reflective electrode 405 (theY direction in FIG. 17) and the alignment direction 407 of the liquidcrystal molecule in the center between the substrates is defined as φ.Display defects (disclination) due to a reverse tilt domain occur in arange of −90°≦φ≦=60° or 60° C.≦φ≦90°, and thus bright, high-qualitytransmissive display is not achieved. A possible reason is formation ofa tilt domain by orthogonal crossing of the alignment direction of theliquid crystal molecule in the center between the substrates and thelongitudinal direction of the reflective electrode. The display defectsformed in the region causes an inevitable increase in the thresholdvoltage during driving of the liquid crystal. Display defects such asdisclination due to the reverse tilt domain are avoidable in a range of−60°≦φ≦60°, and thus bright, high-quality transmissive display isachieved. Since the display defects barely occur, the threshold voltageduring driving of the liquid crystal can be reduced, resulting inreduced power consumption of the liquid crystal device. The aboveadvantage is particularly noticeable in a range of −30°≦φ≦30°.

The effects of the present invention described in the ninth embodimentcan be further ensured by specifying the alignment direction 506 of theliquid crystal molecule in the vicinity of the substrate 502 in FIG. 13.That is, in FIG. 15, an angle between the alignment direction 207 of theliquid crystal molecule in the vicinity of the lower substrate (TFDsubstrate) and the longitudinal direction of the reflective electrode204 is defined as ψ. A preferable angle is in a range of −30°≦ψ≦30°. Ina range outside −30°≦ψ≦30°, the liquid crystal molecule at the substrateinterface is reverse-titled by the effect of the oblique electric fieldto cause display defects.

A table shown in FIG. 20 shows a contrast in a reflective display mode(the ratio of a reflectance at a white display mode to a reflectance ata black display mode) and a contrast in a transmissive display mode (theratio of a transmittance at a white display mode to a transmittance at ablack display mode) when the above-defined angle ψ is varied. In thiscase, the liquid crystal mode is left-twisted by 70 degrees. As shown inthe table in FIG. 20, an angle in a range of −30°≦ψ≦30° is essential forachieving a contrast of 10 or more which is necessary for high-qualityimage display in a reflective display mode and for simultaneouslyachieving a contrast of 5 or more which is necessary for high-qualityimage display in a transmissive display mode. Display defects due toreverse tilt caused by the liquid crystal molecules at the substrateinterface are avoidable in a range of −30°≦ψ≦30°. Also, in FIGS. 16 and17, display defects such as disclination due to a tilt domain areavoidable when the angle ψ between the alignment directions 305 and 408of the liquid crystal molecules at the substrate interfaces and thelongitudinal directions of the reflective electrodes 302 and 405 is in arange of −30° to 30°. The threshold voltage during driving of the liquidcrystal can be reduced, resulting in reduced power consumption of theliquid crystal device. The above advantage is particularly noticeable ina range of −10°≦ψ≦10°.

As in the second to fourth embodiments, the ninth embodiment can includenormally black mode driving, provision of a diffuser, or a reflectiveelectrode with irregularities. In the normally black mode driving, theblack matrix layer 5 a may be omitted.

A tenth embodiment of a liquid crystal device in accordance with thepresent invention will now be described with reference to FIGS. 21 a to23. The tenth embodiment includes a TFD active matrix liquid crystaldevice in accordance with the present invention.

A structure in the vicinity of a TFD driving element, as an example of adiode-type nonlinear element used in this embodiment, will now bedescribed with reference to FIGS. 21 a and 21 b. FIG. 21 a is aschematic plan view of a TFD driving element and a pixel electrode, andFIG. 21 b is a cross-sectional view taken along line B-B′ in FIG. 21 a.In FIG. 21 b, individual layers and elements are depicted at differentscales so that these layers and elements are visible in the drawing.

In FIGS. 21 a and 21 b, A TFD driving element 40 is formed on anunderlying insulating film 41 formed on a transparent substrate 2, iscomposed of a first metal film 42, an insulating layer 44, and a secondmetal film 46, in that order from the side of the insulating film 41,and has a thin film diode (TFD) or metal-insulator-metal (MIM)structure. The first metal film 42 is connected to a scanning line 61formed on the transparent substrate 2, and the second metal film 46 isconnected to a pixel electrode 62 composed of a conductive reflectivefilm as another embodiment of the reflective electrode. In place of thescanning line 61, a data line (described below) may be formed on thetransparent substrate 2, and be connected to the pixel electrode 62, andthe scanning line 61 may be provided on a counter substrate.

The transparent substrate 2 is composed of an insulating transparentsubstrate, for example, glass or plastic. The underlying insulating film41 is composed of, for example, tantalum oxide. The main purpose of theformation of the insulating film 41 is to prevent separation of thefirst metal film 42 from the underlying layer and diffusion ofimpurities from the underlying layer into the first metal film 42 duringheat treatment performed after deposition of the second metal film 46.When the transparent substrate 2 is composed of, for example, a quartzsubstrate having high thermal resistance and high purity which does notcause such separation and diffusion, the insulating film 41 can beomitted. The first metal film 42 is a conductive metal thin filmcomposed of, for example, elemental tantalum or a tantalum alloy. Theinsulating film 44 is composed of, for example, an oxide film which isformed on the first metal film 42 by anodic oxidation in a chemicalsolution. The second metal film 46 is a conductive metal thin filmcomposed of, for example, elemental chromium or a chromium alloy.

In this embodiment, the pixel electrode 62 has regions permittingoptical transmittance, such as oblong or square slits or fine openings,as described in the above embodiments. Alternatively, each pixel issmaller than the transparent electrode on the counter electrode so thatlight passes through a gap therebetween.

A transparent insulating film 29 is provided on a side (the upper facein the drawing) facing the liquid crystal, such as the pixel electrode62, the TFD driving element 40, and the scanning line 61. An alignmentfilm 19 which is composed of an organic thin film such as a polyimidethin film and was subjected to alignment treatment such as rubbing isprovided thereon.

Some examples of a TFD driving element as a diode-type nonlinear elementhave been described above. A diode-type nonlinear element havingbi-directional diode characteristics, such as a zinc oxide (ZnO)varistor, a metal semi-insulator (MSI) driving element or a ring diode(RD), is also applicable to the reflective liquid crystal device in thisembodiment.

The structure and the operation of a TFD active matrix driving-typetransflective liquid crystal device provided with TFD driving elementsin accordance with the tenth embodiment will now be described withreference to FIGS. 22 and 23. FIG. 22 is an equivalent circuit diagramof a liquid crystal device and a driving circuit, and FIG. 23 is apartially broken isometric view for schematically showing the liquidcrystal device.

With reference to FIG. 22, in the TFD active matrix driving-typetransflective liquid crystal device, a plurality of scanning lines 61arranged on a transparent substrate 2 is connected to a Y driver circuit100 constituting a scanning line driving circuit, and a plurality ofdata lines 60 arranged on a counter substrate is connected to an Xdriver circuit 110 constituting a data line driving circuit. The Ydriver circuit 100 and the X driver circuit 110 may be formed on atransparent substrate 2 or a counter substrate. In such a case, thetransflective liquid crystal device is of a driving circuit-integratedtype. Alternatively, the Y driver circuit 100 and the X driver circuit110 are composed of external ICs which may be independent of thetransflective liquid crystal device, and be connected to the scanninglines 61 and the data lines 60 via predetermined lead lines. In thiscase, the transflective liquid crystal device does not have thesedriving circuits.

In each of pixel regions arranged in a matrix, the scanning line 60 isconnected to one terminal of the TFD driving element 40 (See FIGS. 21 aand 21 b), and the data line 60 is connected to the other terminal ofthe TFD driving element 40 via the liquid crystal layer 3 and the pixelelectrode 62. In each pixel region, when scanning signals are suppliedto the respective scanning line 61 while data signals are supplied tothe respective data line 60, the TFD driving element 40 in the pixelregion is turned on so that a driving voltage is applied to the liquidcrystal layer 3 between the pixel electrode 62 and the data line 60 viathe TFD driving element 40. Reflective display is performed byreflection of external light by the pixel electrode 62 in a lightedenvironment, whereas transmissive display is performed by transmissionof light from a backlight as a light source through slits in the pixelelectrode 62 in a dark environment.

In FIG. 23, the transflective liquid crystal device is provided with atransparent substrate 2 and a transparent substrate (counter substrate)1 opposingly arranged thereto. The transparent substrate 1 is composedof, for example, a glass substrate. The transparent substrate 2 isprovided with pixel electrodes 62 arranged in a matrix, and each pixelelectrode 62 is connected to a scanning line 61. The transparentsubstrate 1 is provided with a plurality of rectangular data lines 60 astransparent electrodes extending in the direction perpendicular to thescanning line 61. The data line 60 is composed of, for example, atransparent conductive thin film, such as an indium tin oxide (ITO)film. An alignment film 9 which is composed of an organic thin film suchas a polyimide thin film and was subjected to alignment treatment suchas rubbing is provided below the data line 60. A color filter (not shownin the drawing) composed of color films arranged in a striped, mosaic,or triangle pattern according to use is provided on the transparentsubstrate 1.

As described above, the tenth embodiment can provide a color liquidcrystal device without double imaging and blurred imaging, and which canchange a display mode between a reflective mode and a transmissive mode.In particular, the transflective liquid crystal device can be driven ina normally black mode by voltage control in the X driver circuit 110 andthe Y driver circuit 100 as an example of driving means.

An eleventh embodiment of a liquid crystal device in accordance with thepresent invention will now be described with reference to FIGS. 24 to26. The eleventh embodiment includes a TFT active matrix liquid crystaldevice as a preferable application in accordance with the presentinvention. FIG. 24 is an equivalent circuit diagram of various elementsand lead lines in a plurality of pixels formed in a matrix whichconstitutes an image display region in a liquid crystal device. FIG. 25is a plan view of a plurality of adjacent pixels on a transparentsubstrate provided with data lines, scanning lines and pixel electrodes,and FIG. 26 is a cross-sectional view taken along line C-C′ in FIG. 25.In FIG. 26, individual layers and elements are depicted at differentscales so that these layers and elements are visible in the drawing.

In the TFT active matrix transflective liquid crystal device inaccordance with the eleventh embodiment shown in FIG. 24, a plurality ofTFTs 130 is formed in a matrix and controls pixel electrodes 62 asanother example of reflective electrodes arranged in a matrix. Datalines 135 for supplying image signals are electrically connected tosources of TFTs 130. Image signals S1, S2, . . . , Sn may besequentially supplied to the data lines 135, or may be simultaneouslysupplied to each group consisting of a plurality of adjacent data lines135. The gates of the TFTs 130 are electrically connected to scanninglines 131, and pulse scanning signals G1, G2, . . . , Gm aresequentially supplied to the scanning lines 131 at a given timing. Eachpixel electrode 62 is electrically connected to the drain of the TFT130. The switch of the TFT 130 as a switching element is turned off fora predetermined term so as to input the image signals S1, S2, . . . , Snsupplied from the data lines 135 for a predetermined timing. The imagesignals S1, S2, . . . , Sn which are inputted to the liquid crystal viathe pixel electrodes 62 and have given levels are maintained between thepixel electrode 62 and a counter electrode (described below) formed on acounter electrode (described below) for a predetermined period. Astorage capacitor 170 is provided parallel to the liquid crystalcapacitor formed between the pixel electrode 62 and the counterelectrode in order to prevent leakage of the stored image signals.

In FIG. 25, pixel electrodes 62 (the contour 62 a is shown by dottedlines in the drawing) composed of reflective films are provided in amatrix array on a transparent substrate 2 as a TFT array substrate. Datalines 135, scanning lines 131 and capacitor lines 132 are provided alonghorizontal and vertical boundaries between the pixel electrodes 62. Eachdata line 135 is electrically connected to a source region in asemiconductor layer 81 a composed of a polysilicon film via a contacthole 85. Each pixel electrode 62 is electrically connected to a drainregion in the semiconductor layer 81 a via a contact hole 88. Eachcapacitor line 132 is arranged so as to oppose a first capacitorelectrode extending from the drain region in the semiconductor layer 1 awith an insulating film provided therebetween to form a storagecapacitor 170. Each scanning line 131 is arranged so as to oppose achannel region 81 a′, shown by a shaded region in the drawing, in thesemiconductor layer 81 a, and functions as a gate electrode. Asdescribed above, a TFT 130 with a scanning line 131 as a gate electrodeopposing a channel region 81 a′ is provided at a crossing of a scanningline 131 and a data line 135.

As shown in FIG. 26, the liquid crystal device has a transparentsubstrate 2, and a transparent electrode (counter substrate) 1 opposingthereto. These transparent substrates 1 and 2 are insulating andtransparent substrates composed of quartz, glass, or plastic.

In this embodiment, the pixel electrode 62 has regions permittingoptical transmittance, such as oblong or square slits or fine openings,as described in the above embodiments. Alternatively, each pixel issmaller than the transparent electrode on the counter substrate so thatlight passes through a gap therebetween.

A transparent insulating film 29 is provided on a side (the upper facein the drawing) facing the liquid crystal of the pixel electrode 62 andthe TFT 40. An alignment film 19 which is composed of an organic thinfilm such as a polyimide thin film and was subjected to alignmenttreatment such as rubbing is provided thereon.

The entire face of the transparent substrate 1 is provided with acounter electrode 121 as another example of the transparent electrode,and a second shading film 122 called a black mask or black matrix isprovided in the unopened region of each pixel. An alignment film 9 whichis composed of an organic thin film such as a polyimide film and wassubjected to a given alignment treatment such as rubbing treatment isprovided under the counter electrode 121. A color filter (not shown inthe drawing) composed of color films arranged in a striped, mosaic, ortriangle pattern according to use is provided on the transparentsubstrate 1.

A pixel-switching TFT 130 for controlling by switching each pixelelectrode 62 is provided at a position adjacent to the pixel electrode62 on the transparent substrate 2.

As in the first embodiment, a gap surrounded by a sealant between thepair of first and second substrates 1 and 2 which are disposed so thateach pixel electrode 62 and the counter electrode 121 are opposing eachother is filled with a liquid crystal to form a liquid crystal layer 3.

A first insulating interlayer 112 is provided below the plurality ofpixel-switching TFTs 30. The first insulating interlayer 112 is formedon the entire transparent substrate 2, and functions as an underlyingfilm for the pixel-switching TFTs 30. The first insulating interlayer112 is composed of, for example, a high insulating glass, such asnondoped silicate glass (NSG), phosphosilicate glass (PSG), borosilicateglass (BSG), or borophosphosilicate glass (BPSG); silicon oxide; orsilicon nitride.

In FIG. 26, the pixel-switching TFT 130 includes a source regionconnected to a data line 135 via a contact hole 85, a channel region 81a′ opposing a scanning line 131 and a gate insulating film therebetween,and a drain region connected to the pixel electrode 62 via a contacthole 88. The data line 131 is composed of a light-shading and conductivethin film such as a low resistance metal film, e.g., aluminum, or analloy film such as metal silicide. A second insulating interlayer 114provided with contact holes 85 and 88 is formed thereon, and a thirdinsulating interlayer 117 provided with a contact hole 88 is formedthereon. The second and third insulating interlayers 114 and 117 arealso composed of a high-insulating glass, such as NSG, PSG, BSG, orBPSG, silicon oxide or silicon nitride, as in the first insulatinginterlayer 112.

The pixel-switching TFT 130 may have a LDD structure, an offsetstructure, or a self-aligned structure. The TFT 130 may have a dual gatestructure or a triple gate structure, in addition to a single gatestructure.

According to the TFT active matrix driving-type transflective liquidcrystal device of the eleventh embodiment, as described above, anelectric field is sequentially applied to a liquid crystal portion ateach pixel electrode 62 between the pixel electrode 62 and the counterelectrode 121 to control the alignment state at the liquid crystalportion. Thus, reflective display is performed by reflection of externallight by the pixel electrode 62 in a lighted environment, whereastransmissive display is performed by transmission of light from abacklight as a light source through slits in the pixel electrode 62 in adark environment. Accordingly, a color liquid crystal device withoutdouble imaging and blurred imaging, and which can change a display modebetween a reflective mode and a transmissive mode is achieved. Inparticular, electrical power is supplied to each pixel electrode 62 viathe respective TFT 130; hence, crosstalk between pixel electrodes 62 canbe reduced and high-quality images can be displayed.

The counter electrode on the transparent substrate 1 may be omitted, anddriving may be performed by a transverse electric field, parallel to thesubstrate 1, between pixel electrodes 62 on the transparent substrate.

Color layers of the color filter 5 used in the first to eleventhembodiments will now be described with reference to FIG. 27. FIG. 27 isa graph showing transmittance characteristics of individual color layersin the color filter 5. In a reflective display mode in each embodiment,incident light is transmitted through any one coloring layer of thecolor filter 5, passes through the liquid crystal layer 3, and isreflected by the reflective electrode 7, 17, or 17′, passes through theliquid crystal layer 3 again, and is then emitted. Thus, light passesthrough the color filter two times, unlike in general transmissiveliquid crystal devices. Use of a general color filter, therefore, causesdim display and a reduced contrast. Accordingly, in each embodiment,colors of the R, G, and B coloring layers in the color filter 5 arelighted so as to have a minimum transmittance 61 of 25 to 50% in avisible light region, as shown in FIG. 27. Color lighting of thecoloring layers can be achieved by reducing the thickness of thecoloring layers or by reducing the pigment or dye contents in thecoloring layers. Brightness in a reflective display mode is, thereby,not lowered.

In a transmissive display mode, light passes through the light colorfilter 5 only one time, and thus the displayed image has a lightedcolor. Since the reflective electrode in each embodiment shades a largeamount of light from the backlight, color lighting of the color filter 5is advantageous to securing display brightness.

A twelfth embodiment of the present invention will be described withreference to FIG. 28. The twelfth embodiment pertaining to electronicapparatuses including

liquid crystal device according to any one of the first to eleventhembodiments. That is, the twelfth embodiment includes various electronicapparatuses each using a liquid crystal device shown in any one of thefirst to eleventh embodiments as a display section of the portableapparatuses requiring low power consumption under various environment.FIG. 28 shows three electronic apparatuses in accordance with thepresent invention.

FIG. 28( a) shows a portable phone having a display section 72 providedon the upper front of a body 71. Portable phones are used in variousenvironments including the interior and the exterior. They arefrequently used in automobiles, but the interior of the automobile issignificantly dark at night. A preferable display device used in aportable phone is a transflective liquid crystal device which isprimarily used in a reflective display mode having low power consumptionand is operable in a transmissive display mode using auxiliary light, ifnecessary. Use of a liquid crystal device according to any one of thefirst to eleventh embodiments as a display section 72 of a portablephone yields a portable phone having higher brightness and a highcontrast in both of reflective display mode and transmissive

display mode.

FIG. 28( b) shows a watch having a display section 74 provided in thecenter 73 of the body. An important point in use of the watch is afeeling of luxury. Use of liquid crystal device according to any one ofthe first to eleventh embodiments of the present invention as a displaysection 74 of a watch achieves higher brightness and a high contrast,and reduced coloring due to a small change in properties with thewavelength of light. Thus, color display with a very a luxurious feelingis achieved compared to conventional watches.

FIG. 28( c) shows a portable information apparatus having a displaysection 76 at the upper section and an input section 77 at the lowersection of a body 75. In most cases, touch keys are provided on thefront face of the display section 76. Since conventional touch keys havehigh surface reflectance, it is difficult to see the display. Thus, manyconventional portable apparatuses use transmissive liquid crystaldevices as a display section. Since the transmissive liquid crystaldevice uses a backlight, a large amount of power is consumed and abattery has a shortened life. Use of a liquid crystal device accordingto any one of the first to eleventh embodiments as a display section 76of a portable information apparatus produces a portable informationapparatus having high brightness and clarity in any of reflective,transflective, and transmissive display modes.

The liquid crystal device of the present invention is not limited to theabove embodiments, and can be appropriately modified within the gist andconcept of the present invention in view of claims and the overallspecification. The modified liquid crystal device is also included inthe technical scope of the present invention.

INDUSTRIAL APPLICABILITY

The liquid crystal device in accordance with the present invention canbe used as various display devices which can display bright high-qualityimages in both of dark and lighted environments, and as display sectionsof various electronic apparatuses. Electronic apparatuses using suchliquid crystal devices include liquid crystal televisions, viewfinder-type and monitor-viewing-type videotape recorders, automobilenavigation systems, electronic notebooks, portable calculators,wordprocessors, portable phones, videophones, POS terminals, and touchpanels.

1. A liquid crystal display device comprising: a first transparentsubstrate; second transparent substrate; a liquid crystal layer disposedbetween the first and second substrates; a transparent electrodeinterposed between the first substrate and the liquid crystal; and areflective electrode interposed between the second substrate and theliquid crystal, the reflective electrode overlapping the transparentelectrode to form an overlapping region that has substantially arectangular shape and that extends in a longitudinal direction, thereflective electrode including a rectangular-shaped slit with a longside and a short side, the long side of the slit extending in thelongitudinal direction within the rectangular shape of the overlappingregion.
 2. The liquid crystal display device according to claim 1, thereflective electrode including two or more rectangular-shaped slits thatextend in a lengthwise direction of the reflective electrode.